[PATCH v2 0/2] Accept error packets in any context

[PATCH v2 0/2] Accept error packets in any context

[Masaya Suzuki]

This makes it possible for servers to send an error message back to clients in
an arbitrary situation.

The first patch was originally sent in [1]. This version includes some fix.

The second patch was originally sent in [2]. Later, this was cherry-picked in
[3]. In the discussion in [3], we agreed that this error packet handling should
be done only against the Git pack protocol handling code. With this agreement,
the patch series sent in [3] is abandoned (according to [4]). This is a patch
series based on that agreement on limiting the error packet handling.

[1]: https://public-inbox.org/git/20181227065210.60817-1-masayasuzuki@google.com/
[2]: https://public-inbox.org/git/20181127045301.103807-1-masayasuzuki@google.com/
[3]: https://public-inbox.org/git/df7d3659ae5f11d163f1e992f3b9403be709ddb7.1544572142.git.steadmon@google.com/
[4]: https://public-inbox.org/git/20181213221826.GE37614@google.com/

Masaya Suzuki (2):
  Use packet_reader instead of packet_read_line
  pack-protocol.txt: accept error packets in any context

 Documentation/technical/pack-protocol.txt | 20 +++----
 builtin/archive.c                         | 19 +++----
 builtin/fetch-pack.c                      |  3 +-
 builtin/receive-pack.c                    | 62 +++++++++++----------
 builtin/send-pack.c                       |  3 +-
 connect.c                                 |  3 --
 fetch-pack.c                              | 65 +++++++++++++----------
 pkt-line.c                                |  4 ++
 pkt-line.h                                |  8 ++-
 remote-curl.c                             | 29 ++++++----
 send-pack.c                               | 39 +++++++-------
 serve.c                                   |  5 +-
 t/t5703-upload-pack-ref-in-want.sh        |  4 +-
 transport.c                               |  3 +-
 upload-pack.c                             | 40 +++++++-------
 15 files changed, 174 insertions(+), 133 deletions(-)

-- 
2.20.1.415.g653613c723-goog

[PATCH v2 1/2] Use packet_reader instead of packet_read_line

[Masaya Suzuki]

By using and sharing a packet_reader while handling a Git pack protocol
request, the same reader option is used throughout the code. This makes
it easy to set a reader option to the request parsing code.

Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
---
 builtin/archive.c      | 19 ++++++-------
 builtin/receive-pack.c | 60 +++++++++++++++++++++--------------------
 fetch-pack.c           | 61 +++++++++++++++++++++++-------------------
 remote-curl.c          | 22 ++++++++++-----
 send-pack.c            | 37 ++++++++++++-------------
 upload-pack.c          | 38 +++++++++++++-------------
 6 files changed, 129 insertions(+), 108 deletions(-)

diff --git a/builtin/archive.c b/builtin/archive.c
index d2455237c..2fe1f05ca 100644
--- a/builtin/archive.c
+++ b/builtin/archive.c
@@ -27,10 +27,10 @@ static int run_remote_archiver(int argc, const char **argv,
 			       const char *remote, const char *exec,
 			       const char *name_hint)
 {
-	char *buf;
 	int fd[2], i, rv;
 	struct transport *transport;
 	struct remote *_remote;
+	struct packet_reader reader;
 
 	_remote = remote_get(remote);
 	if (!_remote->url[0])
@@ -53,18 +53,19 @@ static int run_remote_archiver(int argc, const char **argv,
 		packet_write_fmt(fd[1], "argument %s\n", argv[i]);
 	packet_flush(fd[1]);
 
-	buf = packet_read_line(fd[0], NULL);
-	if (!buf)
+	packet_reader_init(&reader, fd[0], NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+
+	if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
 		die(_("git archive: expected ACK/NAK, got a flush packet"));
-	if (strcmp(buf, "ACK")) {
-		if (starts_with(buf, "NACK "))
-			die(_("git archive: NACK %s"), buf + 5);
-		if (starts_with(buf, "ERR "))
-			die(_("remote error: %s"), buf + 4);
+	if (strcmp(reader.line, "ACK")) {
+		if (starts_with(reader.line, "NACK "))
+			die(_("git archive: NACK %s"), reader.line + 5);
+		if (starts_with(reader.line, "ERR "))
+			die(_("remote error: %s"), reader.line + 4);
 		die(_("git archive: protocol error"));
 	}
 
-	if (packet_read_line(fd[0], NULL))
+	if (packet_reader_read(&reader) != PACKET_READ_FLUSH)
 		die(_("git archive: expected a flush"));
 
 	/* Now, start reading from fd[0] and spit it out to stdout */
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 33187bd8e..81cc07370 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1569,30 +1569,29 @@ static void queue_commands_from_cert(struct command **tail,
 	}
 }
 
-static struct command *read_head_info(struct oid_array *shallow)
+static struct command *read_head_info(struct packet_reader *reader,
+				      struct oid_array *shallow)
 {
 	struct command *commands = NULL;
 	struct command **p = &commands;
 	for (;;) {
-		char *line;
-		int len, linelen;
+		int linelen;
 
-		line = packet_read_line(0, &len);
-		if (!line)
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 			break;
 
-		if (len > 8 && starts_with(line, "shallow ")) {
+		if (reader->pktlen > 8 && starts_with(reader->line, "shallow ")) {
 			struct object_id oid;
-			if (get_oid_hex(line + 8, &oid))
+			if (get_oid_hex(reader->line + 8, &oid))
 				die("protocol error: expected shallow sha, got '%s'",
-				    line + 8);
+				    reader->line + 8);
 			oid_array_append(shallow, &oid);
 			continue;
 		}
 
-		linelen = strlen(line);
-		if (linelen < len) {
-			const char *feature_list = line + linelen + 1;
+		linelen = strlen(reader->line);
+		if (linelen < reader->pktlen) {
+			const char *feature_list = reader->line + linelen + 1;
 			if (parse_feature_request(feature_list, "report-status"))
 				report_status = 1;
 			if (parse_feature_request(feature_list, "side-band-64k"))
@@ -1607,28 +1606,32 @@ static struct command *read_head_info(struct oid_array *shallow)
 				use_push_options = 1;
 		}
 
-		if (!strcmp(line, "push-cert")) {
+		if (!strcmp(reader->line, "push-cert")) {
 			int true_flush = 0;
-			char certbuf[1024];
+			int saved_options = reader->options;
+			reader->options &= ~PACKET_READ_CHOMP_NEWLINE;
 
 			for (;;) {
-				len = packet_read(0, NULL, NULL,
-						  certbuf, sizeof(certbuf), 0);
-				if (!len) {
+				packet_reader_read(reader);
+				if (reader->status == PACKET_READ_FLUSH) {
 					true_flush = 1;
 					break;
 				}
-				if (!strcmp(certbuf, "push-cert-end\n"))
+				if (reader->status != PACKET_READ_NORMAL) {
+					die("protocol error: got an unexpected packet");
+				}
+				if (!strcmp(reader->line, "push-cert-end\n"))
 					break; /* end of cert */
-				strbuf_addstr(&push_cert, certbuf);
+				strbuf_addstr(&push_cert, reader->line);
 			}
+			reader->options = saved_options;
 
 			if (true_flush)
 				break;
 			continue;
 		}
 
-		p = queue_command(p, line, linelen);
+		p = queue_command(p, reader->line, linelen);
 	}
 
 	if (push_cert.len)
@@ -1637,18 +1640,14 @@ static struct command *read_head_info(struct oid_array *shallow)
 	return commands;
 }
 
-static void read_push_options(struct string_list *options)
+static void read_push_options(struct packet_reader *reader,
+			      struct string_list *options)
 {
 	while (1) {
-		char *line;
-		int len;
-
-		line = packet_read_line(0, &len);
-
-		if (!line)
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 			break;
 
-		string_list_append(options, line);
+		string_list_append(options, reader->line);
 	}
 }
 
@@ -1924,6 +1923,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 	struct oid_array shallow = OID_ARRAY_INIT;
 	struct oid_array ref = OID_ARRAY_INIT;
 	struct shallow_info si;
+	struct packet_reader reader;
 
 	struct option options[] = {
 		OPT__QUIET(&quiet, N_("quiet")),
@@ -1986,12 +1986,14 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 	if (advertise_refs)
 		return 0;
 
-	if ((commands = read_head_info(&shallow)) != NULL) {
+	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+
+	if ((commands = read_head_info(&reader, &shallow)) != NULL) {
 		const char *unpack_status = NULL;
 		struct string_list push_options = STRING_LIST_INIT_DUP;
 
 		if (use_push_options)
-			read_push_options(&push_options);
+			read_push_options(&reader, &push_options);
 		if (!check_cert_push_options(&push_options)) {
 			struct command *cmd;
 			for (cmd = commands; cmd; cmd = cmd->next)
diff --git a/fetch-pack.c b/fetch-pack.c
index 9691046e6..86790b9bb 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -135,38 +135,42 @@ enum ack_type {
 	ACK_ready
 };
 
-static void consume_shallow_list(struct fetch_pack_args *args, int fd)
+static void consume_shallow_list(struct fetch_pack_args *args,
+				 struct packet_reader *reader)
 {
 	if (args->stateless_rpc && args->deepen) {
 		/* If we sent a depth we will get back "duplicate"
 		 * shallow and unshallow commands every time there
 		 * is a block of have lines exchanged.
 		 */
-		char *line;
-		while ((line = packet_read_line(fd, NULL))) {
-			if (starts_with(line, "shallow "))
+		while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
+			if (starts_with(reader->line, "shallow "))
 				continue;
-			if (starts_with(line, "unshallow "))
+			if (starts_with(reader->line, "unshallow "))
 				continue;
 			die(_("git fetch-pack: expected shallow list"));
 		}
+		if (reader->status != PACKET_READ_FLUSH)
+			die(_("git fetch-pack: expected a flush packet after shallow list"));
 	}
 }
 
-static enum ack_type get_ack(int fd, struct object_id *result_oid)
+static enum ack_type get_ack(struct packet_reader *reader,
+			     struct object_id *result_oid)
 {
 	int len;
-	char *line = packet_read_line(fd, &len);
 	const char *arg;
 
-	if (!line)
+	if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 		die(_("git fetch-pack: expected ACK/NAK, got a flush packet"));
-	if (!strcmp(line, "NAK"))
+	len = reader->pktlen;
+
+	if (!strcmp(reader->line, "NAK"))
 		return NAK;
-	if (skip_prefix(line, "ACK ", &arg)) {
+	if (skip_prefix(reader->line, "ACK ", &arg)) {
 		if (!get_oid_hex(arg, result_oid)) {
 			arg += 40;
-			len -= arg - line;
+			len -= arg - reader->line;
 			if (len < 1)
 				return ACK;
 			if (strstr(arg, "continue"))
@@ -178,9 +182,9 @@ static enum ack_type get_ack(int fd, struct object_id *result_oid)
 			return ACK;
 		}
 	}
-	if (skip_prefix(line, "ERR ", &arg))
+	if (skip_prefix(reader->line, "ERR ", &arg))
 		die(_("remote error: %s"), arg);
-	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), line);
+	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), reader->line);
 }
 
 static void send_request(struct fetch_pack_args *args,
@@ -248,10 +252,14 @@ static int find_common(struct fetch_negotiator *negotiator,
 	int got_ready = 0;
 	struct strbuf req_buf = STRBUF_INIT;
 	size_t state_len = 0;
+	struct packet_reader reader;
 
 	if (args->stateless_rpc && multi_ack == 1)
 		die(_("--stateless-rpc requires multi_ack_detailed"));
 
+	packet_reader_init(&reader, fd[0], NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE);
+
 	if (!args->no_dependents) {
 		mark_tips(negotiator, args->negotiation_tips);
 		for_each_cached_alternate(negotiator, insert_one_alternate_object);
@@ -336,31 +344,30 @@ static int find_common(struct fetch_negotiator *negotiator,
 	state_len = req_buf.len;
 
 	if (args->deepen) {
-		char *line;
 		const char *arg;
 		struct object_id oid;
 
 		send_request(args, fd[1], &req_buf);
-		while ((line = packet_read_line(fd[0], NULL))) {
-			if (skip_prefix(line, "shallow ", &arg)) {
+		while (packet_reader_read(&reader) == PACKET_READ_NORMAL) {
+			if (skip_prefix(reader.line, "shallow ", &arg)) {
 				if (get_oid_hex(arg, &oid))
-					die(_("invalid shallow line: %s"), line);
+					die(_("invalid shallow line: %s"), reader.line);
 				register_shallow(the_repository, &oid);
 				continue;
 			}
-			if (skip_prefix(line, "unshallow ", &arg)) {
+			if (skip_prefix(reader.line, "unshallow ", &arg)) {
 				if (get_oid_hex(arg, &oid))
-					die(_("invalid unshallow line: %s"), line);
+					die(_("invalid unshallow line: %s"), reader.line);
 				if (!lookup_object(the_repository, oid.hash))
-					die(_("object not found: %s"), line);
+					die(_("object not found: %s"), reader.line);
 				/* make sure that it is parsed as shallow */
 				if (!parse_object(the_repository, &oid))
-					die(_("error in object: %s"), line);
+					die(_("error in object: %s"), reader.line);
 				if (unregister_shallow(&oid))
-					die(_("no shallow found: %s"), line);
+					die(_("no shallow found: %s"), reader.line);
 				continue;
 			}
-			die(_("expected shallow/unshallow, got %s"), line);
+			die(_("expected shallow/unshallow, got %s"), reader.line);
 		}
 	} else if (!args->stateless_rpc)
 		send_request(args, fd[1], &req_buf);
@@ -397,9 +404,9 @@ static int find_common(struct fetch_negotiator *negotiator,
 			if (!args->stateless_rpc && count == INITIAL_FLUSH)
 				continue;
 
-			consume_shallow_list(args, fd[0]);
+			consume_shallow_list(args, &reader);
 			do {
-				ack = get_ack(fd[0], result_oid);
+				ack = get_ack(&reader, result_oid);
 				if (ack)
 					print_verbose(args, _("got %s %d %s"), "ack",
 						      ack, oid_to_hex(result_oid));
@@ -469,9 +476,9 @@ static int find_common(struct fetch_negotiator *negotiator,
 	strbuf_release(&req_buf);
 
 	if (!got_ready || !no_done)
-		consume_shallow_list(args, fd[0]);
+		consume_shallow_list(args, &reader);
 	while (flushes || multi_ack) {
-		int ack = get_ack(fd[0], result_oid);
+		int ack = get_ack(&reader, result_oid);
 		if (ack) {
 			print_verbose(args, _("got %s (%d) %s"), "ack",
 				      ack, oid_to_hex(result_oid));
diff --git a/remote-curl.c b/remote-curl.c
index 1220dffcd..bbd9ba0f3 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -409,28 +409,36 @@ static struct discovery *discover_refs(const char *service, int for_push)
 	if (maybe_smart &&
 	    (5 <= last->len && last->buf[4] == '#') &&
 	    !strbuf_cmp(&exp, &type)) {
-		char *line;
+		struct packet_reader reader;
+		packet_reader_init(&reader, -1, last->buf, last->len,
+				   PACKET_READ_CHOMP_NEWLINE);
 
 		/*
 		 * smart HTTP response; validate that the service
 		 * pkt-line matches our request.
 		 */
-		line = packet_read_line_buf(&last->buf, &last->len, NULL);
-		if (!line)
+		if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
 			die("invalid server response; expected service, got flush packet");
 
 		strbuf_reset(&exp);
 		strbuf_addf(&exp, "# service=%s", service);
-		if (strcmp(line, exp.buf))
-			die("invalid server response; got '%s'", line);
+		if (strcmp(reader.line, exp.buf))
+			die("invalid server response; got '%s'", reader.line);
 		strbuf_release(&exp);
 
 		/* The header can include additional metadata lines, up
 		 * until a packet flush marker.  Ignore these now, but
 		 * in the future we might start to scan them.
 		 */
-		while (packet_read_line_buf(&last->buf, &last->len, NULL))
-			;
+		for (;;) {
+			packet_reader_read(&reader);
+			if (reader.pktlen <= 0) {
+				break;
+			}
+		}
+
+		last->buf = reader.src_buffer;
+		last->len = reader.src_len;
 
 		last->proto_git = 1;
 	} else if (maybe_smart &&
diff --git a/send-pack.c b/send-pack.c
index f69268677..913645046 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -135,38 +135,36 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struc
 	return 0;
 }
 
-static int receive_unpack_status(int in)
+static int receive_unpack_status(struct packet_reader *reader)
 {
-	const char *line = packet_read_line(in, NULL);
-	if (!line)
+	if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 		return error(_("unexpected flush packet while reading remote unpack status"));
-	if (!skip_prefix(line, "unpack ", &line))
-		return error(_("unable to parse remote unpack status: %s"), line);
-	if (strcmp(line, "ok"))
-		return error(_("remote unpack failed: %s"), line);
+	if (!skip_prefix(reader->line, "unpack ", &reader->line))
+		return error(_("unable to parse remote unpack status: %s"), reader->line);
+	if (strcmp(reader->line, "ok"))
+		return error(_("remote unpack failed: %s"), reader->line);
 	return 0;
 }
 
-static int receive_status(int in, struct ref *refs)
+static int receive_status(struct packet_reader *reader, struct ref *refs)
 {
 	struct ref *hint;
 	int ret;
 
 	hint = NULL;
-	ret = receive_unpack_status(in);
+	ret = receive_unpack_status(reader);
 	while (1) {
-		char *refname;
+		const char *refname;
 		char *msg;
-		char *line = packet_read_line(in, NULL);
-		if (!line)
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 			break;
-		if (!starts_with(line, "ok ") && !starts_with(line, "ng ")) {
-			error("invalid ref status from remote: %s", line);
+		if (!starts_with(reader->line, "ok ") && !starts_with(reader->line, "ng ")) {
+			error("invalid ref status from remote: %s", reader->line);
 			ret = -1;
 			break;
 		}
 
-		refname = line + 3;
+		refname = reader->line + 3;
 		msg = strchr(refname, ' ');
 		if (msg)
 			*msg++ = '\0';
@@ -187,7 +185,7 @@ static int receive_status(int in, struct ref *refs)
 			continue;
 		}
 
-		if (line[0] == 'o' && line[1] == 'k')
+		if (reader->line[0] == 'o' && reader->line[1] == 'k')
 			hint->status = REF_STATUS_OK;
 		else {
 			hint->status = REF_STATUS_REMOTE_REJECT;
@@ -390,6 +388,7 @@ int send_pack(struct send_pack_args *args,
 	int ret;
 	struct async demux;
 	const char *push_cert_nonce = NULL;
+	struct packet_reader reader;
 
 	/* Does the other end support the reporting? */
 	if (server_supports("report-status"))
@@ -559,6 +558,8 @@ int send_pack(struct send_pack_args *args,
 		in = demux.out;
 	}
 
+	packet_reader_init(&reader, in, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+
 	if (need_pack_data && cmds_sent) {
 		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
 			for (ref = remote_refs; ref; ref = ref->next)
@@ -573,7 +574,7 @@ int send_pack(struct send_pack_args *args,
 			 * are failing, and just want the error() side effects.
 			 */
 			if (status_report)
-				receive_unpack_status(in);
+				receive_unpack_status(&reader);
 
 			if (use_sideband) {
 				close(demux.out);
@@ -590,7 +591,7 @@ int send_pack(struct send_pack_args *args,
 		packet_flush(out);
 
 	if (status_report && cmds_sent)
-		ret = receive_status(in, remote_refs);
+		ret = receive_status(&reader, remote_refs);
 	else
 		ret = 0;
 	if (args->stateless_rpc)
diff --git a/upload-pack.c b/upload-pack.c
index 5e81f1ff2..1638825ee 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -354,7 +354,8 @@ static int ok_to_give_up(const struct object_array *have_obj,
 					    min_generation);
 }
 
-static int get_common_commits(struct object_array *have_obj,
+static int get_common_commits(struct packet_reader *reader,
+			      struct object_array *have_obj,
 			      struct object_array *want_obj)
 {
 	struct object_id oid;
@@ -366,12 +367,11 @@ static int get_common_commits(struct object_array *have_obj,
 	save_commit_buffer = 0;
 
 	for (;;) {
-		char *line = packet_read_line(0, NULL);
 		const char *arg;
 
 		reset_timeout();
 
-		if (!line) {
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL) {
 			if (multi_ack == 2 && got_common
 			    && !got_other && ok_to_give_up(have_obj, want_obj)) {
 				sent_ready = 1;
@@ -390,7 +390,7 @@ static int get_common_commits(struct object_array *have_obj,
 			got_other = 0;
 			continue;
 		}
-		if (skip_prefix(line, "have ", &arg)) {
+		if (skip_prefix(reader->line, "have ", &arg)) {
 			switch (got_oid(arg, &oid, have_obj)) {
 			case -1: /* they have what we do not */
 				got_other = 1;
@@ -416,7 +416,7 @@ static int get_common_commits(struct object_array *have_obj,
 			}
 			continue;
 		}
-		if (!strcmp(line, "done")) {
+		if (!strcmp(reader->line, "done")) {
 			if (have_obj->nr > 0) {
 				if (multi_ack)
 					packet_write_fmt(1, "ACK %s\n", last_hex);
@@ -425,7 +425,7 @@ static int get_common_commits(struct object_array *have_obj,
 			packet_write_fmt(1, "NAK\n");
 			return -1;
 		}
-		die("git upload-pack: expected SHA1 list, got '%s'", line);
+		die("git upload-pack: expected SHA1 list, got '%s'", reader->line);
 	}
 }
 
@@ -826,7 +826,7 @@ static int process_deepen_not(const char *line, struct string_list *deepen_not,
 	return 0;
 }
 
-static void receive_needs(struct object_array *want_obj)
+static void receive_needs(struct packet_reader *reader, struct object_array *want_obj)
 {
 	struct object_array shallows = OBJECT_ARRAY_INIT;
 	struct string_list deepen_not = STRING_LIST_INIT_DUP;
@@ -840,33 +840,32 @@ static void receive_needs(struct object_array *want_obj)
 		struct object *o;
 		const char *features;
 		struct object_id oid_buf;
-		char *line = packet_read_line(0, NULL);
 		const char *arg;
 
 		reset_timeout();
-		if (!line)
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 			break;
 
-		if (process_shallow(line, &shallows))
+		if (process_shallow(reader->line, &shallows))
 			continue;
-		if (process_deepen(line, &depth))
+		if (process_deepen(reader->line, &depth))
 			continue;
-		if (process_deepen_since(line, &deepen_since, &deepen_rev_list))
+		if (process_deepen_since(reader->line, &deepen_since, &deepen_rev_list))
 			continue;
-		if (process_deepen_not(line, &deepen_not, &deepen_rev_list))
+		if (process_deepen_not(reader->line, &deepen_not, &deepen_rev_list))
 			continue;
 
-		if (skip_prefix(line, "filter ", &arg)) {
+		if (skip_prefix(reader->line, "filter ", &arg)) {
 			if (!filter_capability_requested)
 				die("git upload-pack: filtering capability not negotiated");
 			parse_list_objects_filter(&filter_options, arg);
 			continue;
 		}
 
-		if (!skip_prefix(line, "want ", &arg) ||
+		if (!skip_prefix(reader->line, "want ", &arg) ||
 		    parse_oid_hex(arg, &oid_buf, &features))
 			die("git upload-pack: protocol error, "
-			    "expected to get object ID, not '%s'", line);
+			    "expected to get object ID, not '%s'", reader->line);
 
 		if (parse_feature_request(features, "deepen-relative"))
 			deepen_relative = 1;
@@ -1055,6 +1054,7 @@ void upload_pack(struct upload_pack_options *options)
 {
 	struct string_list symref = STRING_LIST_INIT_DUP;
 	struct object_array want_obj = OBJECT_ARRAY_INIT;
+	struct packet_reader reader;
 
 	stateless_rpc = options->stateless_rpc;
 	timeout = options->timeout;
@@ -1078,10 +1078,12 @@ void upload_pack(struct upload_pack_options *options)
 	if (options->advertise_refs)
 		return;
 
-	receive_needs(&want_obj);
+	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+
+	receive_needs(&reader, &want_obj);
 	if (want_obj.nr) {
 		struct object_array have_obj = OBJECT_ARRAY_INIT;
-		get_common_commits(&have_obj, &want_obj);
+		get_common_commits(&reader, &have_obj, &want_obj);
 		create_pack_file(&have_obj, &want_obj);
 	}
 }
-- 
2.20.1.415.g653613c723-goog

[PATCH v2 2/2] pack-protocol.txt: accept error packets in any context

[Masaya Suzuki]

In the Git pack protocol definition, an error packet may appear only in
a certain context. However, servers can face a runtime error (e.g. I/O
error) at an arbitrary timing. This patch changes the protocol to allow
an error packet to be sent instead of any packet.

Without this protocol spec change, when a server cannot process a
request, there's no way to tell that to a client. Since the server
cannot produce a valid response, it would be forced to cut a connection
without telling why. With this protocol spec change, the server can be
more gentle in this situation. An old client may see these error packets
as an unexpected packet, but this is not worse than having an unexpected
EOF.

Following this protocol spec change, the error packet handling code is
moved to pkt-line.c. Implementation wise, this implementation uses
pkt-line to communicate with a subprocess. Since this is not a part of
Git protocol, it's possible that a packet that is not supposed to be an
error packet is mistakenly parsed as an error packet. This error packet
handling is enabled only for the Git pack protocol parsing code
considering this.

Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
---
 Documentation/technical/pack-protocol.txt | 20 +++++++++++---------
 builtin/archive.c                         |  6 +++---
 builtin/fetch-pack.c                      |  3 ++-
 builtin/receive-pack.c                    |  4 +++-
 builtin/send-pack.c                       |  3 ++-
 connect.c                                 |  3 ---
 fetch-pack.c                              |  8 ++++----
 pkt-line.c                                |  4 ++++
 pkt-line.h                                |  8 ++++++--
 remote-curl.c                             |  9 ++++++---
 send-pack.c                               |  4 +++-
 serve.c                                   |  5 +++--
 t/t5703-upload-pack-ref-in-want.sh        |  4 ++--
 transport.c                               |  3 ++-
 upload-pack.c                             |  4 +++-
 15 files changed, 54 insertions(+), 34 deletions(-)

diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index 6ac774d5f..7a2375a55 100644
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -22,6 +22,16 @@ protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless
 otherwise noted the usual pkt-line LF rules apply: the sender SHOULD
 include a LF, but the receiver MUST NOT complain if it is not present.
 
+An error packet is a special pkt-line that contains an error string.
+
+----
+  error-line     =  PKT-LINE("ERR" SP explanation-text)
+----
+
+Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY
+be sent. Once this packet is sent by a client or a server, the data transfer
+process defined in this protocol is terminated.
+
 Transports
 ----------
 There are three transports over which the packfile protocol is
@@ -89,13 +99,6 @@ process on the server side over the Git protocol is this:
      "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" |
      nc -v example.com 9418
 
-If the server refuses the request for some reasons, it could abort
-gracefully with an error message.
-
-----
-  error-line     =  PKT-LINE("ERR" SP explanation-text)
-----
-
 
 SSH Transport
 -------------
@@ -398,12 +401,11 @@ from the client).
 Then the server will start sending its packfile data.
 
 ----
-  server-response = *ack_multi ack / nak / error-line
+  server-response = *ack_multi ack / nak
   ack_multi       = PKT-LINE("ACK" SP obj-id ack_status)
   ack_status      = "continue" / "common" / "ready"
   ack             = PKT-LINE("ACK" SP obj-id)
   nak             = PKT-LINE("NAK")
-  error-line     =  PKT-LINE("ERR" SP explanation-text)
 ----
 
 A simple clone may look like this (with no 'have' lines):
diff --git a/builtin/archive.c b/builtin/archive.c
index 2fe1f05ca..45d11669a 100644
--- a/builtin/archive.c
+++ b/builtin/archive.c
@@ -53,15 +53,15 @@ static int run_remote_archiver(int argc, const char **argv,
 		packet_write_fmt(fd[1], "argument %s\n", argv[i]);
 	packet_flush(fd[1]);
 
-	packet_reader_init(&reader, fd[0], NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+	packet_reader_init(&reader, fd[0], NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
 		die(_("git archive: expected ACK/NAK, got a flush packet"));
 	if (strcmp(reader.line, "ACK")) {
 		if (starts_with(reader.line, "NACK "))
 			die(_("git archive: NACK %s"), reader.line + 5);
-		if (starts_with(reader.line, "ERR "))
-			die(_("remote error: %s"), reader.line + 4);
 		die(_("git archive: protocol error"));
 	}
 
diff --git a/builtin/fetch-pack.c b/builtin/fetch-pack.c
index 63e69a580..85dbc2af8 100644
--- a/builtin/fetch-pack.c
+++ b/builtin/fetch-pack.c
@@ -217,7 +217,8 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
 
 	packet_reader_init(&reader, fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	switch (discover_version(&reader)) {
 	case protocol_v2:
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 81cc07370..d58b7750b 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1986,7 +1986,9 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 	if (advertise_refs)
 		return 0;
 
-	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+	packet_reader_init(&reader, 0, NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if ((commands = read_head_info(&reader, &shallow)) != NULL) {
 		const char *unpack_status = NULL;
diff --git a/builtin/send-pack.c b/builtin/send-pack.c
index 8e3c7490f..098ebf22d 100644
--- a/builtin/send-pack.c
+++ b/builtin/send-pack.c
@@ -250,7 +250,8 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
 
 	packet_reader_init(&reader, fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	switch (discover_version(&reader)) {
 	case protocol_v2:
diff --git a/connect.c b/connect.c
index 24281b608..4813f005a 100644
--- a/connect.c
+++ b/connect.c
@@ -296,7 +296,6 @@ struct ref **get_remote_heads(struct packet_reader *reader,
 	struct ref **orig_list = list;
 	int len = 0;
 	enum get_remote_heads_state state = EXPECTING_FIRST_REF;
-	const char *arg;
 
 	*list = NULL;
 
@@ -306,8 +305,6 @@ struct ref **get_remote_heads(struct packet_reader *reader,
 			die_initial_contact(1);
 		case PACKET_READ_NORMAL:
 			len = reader->pktlen;
-			if (len > 4 && skip_prefix(reader->line, "ERR ", &arg))
-				die(_("remote error: %s"), arg);
 			break;
 		case PACKET_READ_FLUSH:
 			state = EXPECTING_DONE;
diff --git a/fetch-pack.c b/fetch-pack.c
index 86790b9bb..3f9626dbf 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -182,8 +182,6 @@ static enum ack_type get_ack(struct packet_reader *reader,
 			return ACK;
 		}
 	}
-	if (skip_prefix(reader->line, "ERR ", &arg))
-		die(_("remote error: %s"), arg);
 	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), reader->line);
 }
 
@@ -258,7 +256,8 @@ static int find_common(struct fetch_negotiator *negotiator,
 		die(_("--stateless-rpc requires multi_ack_detailed"));
 
 	packet_reader_init(&reader, fd[0], NULL, 0,
-			   PACKET_READ_CHOMP_NEWLINE);
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if (!args->no_dependents) {
 		mark_tips(negotiator, args->negotiation_tips);
@@ -1358,7 +1357,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	struct fetch_negotiator negotiator;
 	fetch_negotiator_init(&negotiator, negotiation_algorithm);
 	packet_reader_init(&reader, fd[0], NULL, 0,
-			   PACKET_READ_CHOMP_NEWLINE);
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	while (state != FETCH_DONE) {
 		switch (state) {
diff --git a/pkt-line.c b/pkt-line.c
index 04d10bbd0..e70ea6d88 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -346,6 +346,10 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 		return PACKET_READ_EOF;
 	}
 
+	if ((options & PACKET_READ_DIE_ON_ERR_PACKET) &&
+	    starts_with(buffer, "ERR "))
+		die(_("remote error: %s"), buffer + 4);
+
 	if ((options & PACKET_READ_CHOMP_NEWLINE) &&
 	    len && buffer[len-1] == '\n')
 		len--;
diff --git a/pkt-line.h b/pkt-line.h
index 5b28d4347..d7e1dbc04 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -62,9 +62,13 @@ int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
  *
  * If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
  * present) is removed from the buffer before returning.
+ *
+ * If options contains PACKET_READ_DIE_ON_ERR_PACKET, it dies when it sees an
+ * ERR packet.
  */
-#define PACKET_READ_GENTLE_ON_EOF (1u<<0)
-#define PACKET_READ_CHOMP_NEWLINE (1u<<1)
+#define PACKET_READ_GENTLE_ON_EOF     (1u<<0)
+#define PACKET_READ_CHOMP_NEWLINE     (1u<<1)
+#define PACKET_READ_DIE_ON_ERR_PACKET (1u<<2)
 int packet_read(int fd, char **src_buffer, size_t *src_len, char
 		*buffer, unsigned size, int options);
 
diff --git a/remote-curl.c b/remote-curl.c
index bbd9ba0f3..10b50869c 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -204,7 +204,8 @@ static struct ref *parse_git_refs(struct discovery *heads, int for_push)
 
 	packet_reader_init(&reader, -1, heads->buf, heads->len,
 			   PACKET_READ_CHOMP_NEWLINE |
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	heads->version = discover_version(&reader);
 	switch (heads->version) {
@@ -411,7 +412,8 @@ static struct discovery *discover_refs(const char *service, int for_push)
 	    !strbuf_cmp(&exp, &type)) {
 		struct packet_reader reader;
 		packet_reader_init(&reader, -1, last->buf, last->len,
-				   PACKET_READ_CHOMP_NEWLINE);
+				   PACKET_READ_CHOMP_NEWLINE |
+				   PACKET_READ_DIE_ON_ERR_PACKET);
 
 		/*
 		 * smart HTTP response; validate that the service
@@ -1182,7 +1184,8 @@ static void proxy_state_init(struct proxy_state *p, const char *service_name,
 		p->headers = curl_slist_append(p->headers, buf.buf);
 
 	packet_reader_init(&p->reader, p->in, NULL, 0,
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	strbuf_release(&buf);
 }
diff --git a/send-pack.c b/send-pack.c
index 913645046..7b9829f16 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -558,7 +558,9 @@ int send_pack(struct send_pack_args *args,
 		in = demux.out;
 	}
 
-	packet_reader_init(&reader, in, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+	packet_reader_init(&reader, in, NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	if (need_pack_data && cmds_sent) {
 		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
diff --git a/serve.c b/serve.c
index bda085f09..317256c1a 100644
--- a/serve.c
+++ b/serve.c
@@ -167,7 +167,8 @@ static int process_request(void)
 
 	packet_reader_init(&reader, 0, NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	/*
 	 * Check to see if the client closed their end before sending another
@@ -175,7 +176,7 @@ static int process_request(void)
 	 */
 	if (packet_reader_peek(&reader) == PACKET_READ_EOF)
 		return 1;
-	reader.options = PACKET_READ_CHOMP_NEWLINE;
+	reader.options &= ~PACKET_READ_GENTLE_ON_EOF;
 
 	while (state != PROCESS_REQUEST_DONE) {
 		switch (packet_reader_peek(&reader)) {
diff --git a/t/t5703-upload-pack-ref-in-want.sh b/t/t5703-upload-pack-ref-in-want.sh
index 3f58f05cb..d2a9d0c12 100755
--- a/t/t5703-upload-pack-ref-in-want.sh
+++ b/t/t5703-upload-pack-ref-in-want.sh
@@ -208,7 +208,7 @@ test_expect_success 'server is initially ahead - no ref in want' '
 	cp -r "$LOCAL_PRISTINE" local &&
 	inconsistency master 1234567890123456789012345678901234567890 &&
 	test_must_fail git -C local fetch 2>err &&
-	grep "ERR upload-pack: not our ref" err
+	grep "fatal: remote error: upload-pack: not our ref" err
 '
 
 test_expect_success 'server is initially ahead - ref in want' '
@@ -254,7 +254,7 @@ test_expect_success 'server loses a ref - ref in want' '
 	echo "s/master/raster/" >"$HTTPD_ROOT_PATH/one-time-sed" &&
 	test_must_fail git -C local fetch 2>err &&
 
-	grep "ERR unknown ref refs/heads/raster" err
+	grep "fatal: remote error: unknown ref refs/heads/raster" err
 '
 
 stop_httpd
diff --git a/transport.c b/transport.c
index 5a74b609f..12db4251c 100644
--- a/transport.c
+++ b/transport.c
@@ -273,7 +273,8 @@ static struct ref *handshake(struct transport *transport, int for_push,
 
 	packet_reader_init(&reader, data->fd[0], NULL, 0,
 			   PACKET_READ_CHOMP_NEWLINE |
-			   PACKET_READ_GENTLE_ON_EOF);
+			   PACKET_READ_GENTLE_ON_EOF |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	data->version = discover_version(&reader);
 	switch (data->version) {
diff --git a/upload-pack.c b/upload-pack.c
index 1638825ee..08b547cf0 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -1078,7 +1078,9 @@ void upload_pack(struct upload_pack_options *options)
 	if (options->advertise_refs)
 		return;
 
-	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
+	packet_reader_init(&reader, 0, NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE |
+			   PACKET_READ_DIE_ON_ERR_PACKET);
 
 	receive_needs(&reader, &want_obj);
 	if (want_obj.nr) {
-- 
2.20.1.415.g653613c723-goog

Re: [PATCH v2 0/2] Accept error packets in any context

[Junio C Hamano]

Masaya Suzuki <masayasuzuki@google.com> writes:

> This makes it possible for servers to send an error message back to clients in
> an arbitrary situation.
>
> The first patch was originally sent in [1]. This version includes some fix.
>
> The second patch was originally sent in [2]. Later, this was cherry-picked in
> [3]. In the discussion in [3], we agreed that this error packet handling should
> be done only against the Git pack protocol handling code. With this agreement,
> the patch series sent in [3] is abandoned (according to [4]). This is a patch
> series based on that agreement on limiting the error packet handling.

In short, are you shooting js/smart-http-detect-remote-error topic
down and replacing it with this one?

As that topic is not yet in 'next', I am perfectly fine doing that.
I just want to make sure that is what you meant, as my reading of
[4] was a bit fuzzy.

Thanks.

>
> [1]: https://public-inbox.org/git/20181227065210.60817-1-masayasuzuki@google.com/
> [2]: https://public-inbox.org/git/20181127045301.103807-1-masayasuzuki@google.com/
> [3]: https://public-inbox.org/git/df7d3659ae5f11d163f1e992f3b9403be709ddb7.1544572142.git.steadmon@google.com/
> [4]: https://public-inbox.org/git/20181213221826.GE37614@google.com/
>
> Masaya Suzuki (2):
>   Use packet_reader instead of packet_read_line
>   pack-protocol.txt: accept error packets in any context

Re: [PATCH v2 0/2] Accept error packets in any context

[Masaya Suzuki]

On Thu, Jan 3, 2019 at 3:05 PM Junio C Hamano <gitster@pobox.com> wrote:
>
> Masaya Suzuki <masayasuzuki@google.com> writes:
>
> > This makes it possible for servers to send an error message back to clients in
> > an arbitrary situation.
> >
> > The first patch was originally sent in [1]. This version includes some fix.
> >
> > The second patch was originally sent in [2]. Later, this was cherry-picked in
> > [3]. In the discussion in [3], we agreed that this error packet handling should
> > be done only against the Git pack protocol handling code. With this agreement,
> > the patch series sent in [3] is abandoned (according to [4]). This is a patch
> > series based on that agreement on limiting the error packet handling.
>
> In short, are you shooting js/smart-http-detect-remote-error topic
> down and replacing it with this one?
>
> As that topic is not yet in 'next', I am perfectly fine doing that.
> I just want to make sure that is what you meant, as my reading of
> [4] was a bit fuzzy.

Sorry, I think I referenced a wrong email. [4] was meant to be
https://public-inbox.org/git/20181219233005.GI37614@google.com/. I
think he wants to have
https://public-inbox.org/git/20181116084725.GA31603@sigill.intra.peff.net/,
https://public-inbox.org/git/20181116084838.GB31603@sigill.intra.peff.net/,
and https://public-inbox.org/git/20181116084951.GC31603@sigill.intra.peff.net/
for js/smart-http-detect-remote-error.

Re: [PATCH v2 1/2] Use packet_reader instead of packet_read_line

[Jonathan Tan]

> By using and sharing a packet_reader while handling a Git pack protocol
> request, the same reader option is used throughout the code. This makes
> it easy to set a reader option to the request parsing code.

I see that packet_read() and packet_read_line_buf() invocations are also
removed, so it might be better to use "Use packet_reader instead of
packet_read.*" as the commit title.

The code looks correct to me - most of the changes are removals of
packet_read_line(), replaced with a packet_reader that has
PACKET_READ_CHOMP_NEWLINE. One instance is packet_read(), for which the
corresponding reader does not have PACKET_READ_CHOMP_NEWLINE (noted
below); and another instance is packet_read_line_buf(), for which the
corresponding reader is instantiated accordingly with the buffer (also
noted below).

> -		if (!strcmp(line, "push-cert")) {
> +		if (!strcmp(reader->line, "push-cert")) {
>  			int true_flush = 0;
> -			char certbuf[1024];
> +			int saved_options = reader->options;
> +			reader->options &= ~PACKET_READ_CHOMP_NEWLINE;
>  
>  			for (;;) {
> -				len = packet_read(0, NULL, NULL,
> -						  certbuf, sizeof(certbuf), 0);
> -				if (!len) {
> +				packet_reader_read(reader);
> +				if (reader->status == PACKET_READ_FLUSH) {
>  					true_flush = 1;
>  					break;
>  				}
> -				if (!strcmp(certbuf, "push-cert-end\n"))
> +				if (reader->status != PACKET_READ_NORMAL) {
> +					die("protocol error: got an unexpected packet");
> +				}
> +				if (!strcmp(reader->line, "push-cert-end\n"))
>  					break; /* end of cert */
> -				strbuf_addstr(&push_cert, certbuf);
> +				strbuf_addstr(&push_cert, reader->line);
>  			}
> +			reader->options = saved_options;

Here, packet_read() is used, so we shouldn't chomp the newline, so this
is correct.

> -		char *line;
> +		struct packet_reader reader;
> +		packet_reader_init(&reader, -1, last->buf, last->len,
> +				   PACKET_READ_CHOMP_NEWLINE);
>  
>  		/*
>  		 * smart HTTP response; validate that the service
>  		 * pkt-line matches our request.
>  		 */
> -		line = packet_read_line_buf(&last->buf, &last->len, NULL);
> -		if (!line)
> +		if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
>  			die("invalid server response; expected service, got flush packet");
>  
>  		strbuf_reset(&exp);
>  		strbuf_addf(&exp, "# service=%s", service);
> -		if (strcmp(line, exp.buf))
> -			die("invalid server response; got '%s'", line);
> +		if (strcmp(reader.line, exp.buf))
> +			die("invalid server response; got '%s'", reader.line);
>  		strbuf_release(&exp);
>  
>  		/* The header can include additional metadata lines, up
>  		 * until a packet flush marker.  Ignore these now, but
>  		 * in the future we might start to scan them.
>  		 */
> -		while (packet_read_line_buf(&last->buf, &last->len, NULL))
> -			;
> +		for (;;) {
> +			packet_reader_read(&reader);
> +			if (reader.pktlen <= 0) {
> +				break;
> +			}
> +		}
> +
> +		last->buf = reader.src_buffer;
> +		last->len = reader.src_len;

And here, packet_reader_init() correctly initializes the packet_reader
with the buffer, and we need to know where in the buffer to continue
after parsing the additional metadata lines and the packet flush, so we
assign the state of the reader to last->buf and last->len.

(Incidentally, with this change, there is no longer any usage of
packet_read_line_buf(), but we can remove that in a subsequent patch.)

In summary, this looks like a good change. Configuration of reader
metadata (file descriptors, input buffers, and flags) is now more
centralized, and there are fewer file descriptor constants and variables
(which all look like ints) strewn around.

Re: [PATCH v2 2/2] pack-protocol.txt: accept error packets in any context

[Jonathan Tan]

First of all, there was some discussion [1] about its relation with
js/smart-http-detect-remote-error. I noticed that
js/smart-http-detect-remote-error has all tests passing even if I remove
Masaya's patch, so I'm reviewing these patches independently, directly on
master.

[1] https://public-inbox.org/git/CAJB1erU0utjKGtv3LBFT6SEEKCfFRuxGvDtpkKeS3GSC1S89JA@mail.gmail.com/

> In the Git pack protocol definition, an error packet may appear only in
> a certain context. However, servers can face a runtime error (e.g. I/O
> error) at an arbitrary timing. This patch changes the protocol to allow
> an error packet to be sent instead of any packet.
> 
> Without this protocol spec change, when a server cannot process a
> request, there's no way to tell that to a client. Since the server
> cannot produce a valid response, it would be forced to cut a connection
> without telling why. With this protocol spec change, the server can be
> more gentle in this situation. An old client may see these error packets
> as an unexpected packet, but this is not worse than having an unexpected
> EOF.

The other thing that happens is that servers send "ERR" anyway, even
though it is not allowed by the protocol.

This overall looks like a good direction - this makes explicit something
that is already being done.

My remaining concern is if "ERR " could be a non-error packet mistaken
for an error one. I glanced through pack-protocol.txt and as far as I
can tell, I don't see anything non-error sent by the server that could
be prefixed with "ERR". (There are push-option and gpg-signature-lines,
but those are sent by the client.) Packfiles can contain anything, of
course, but as far as I can tell, they are either sent un-PKT-ed or
preceded by a sideband (\1), so they are fine.

> diff --git a/serve.c b/serve.c
> index bda085f09..317256c1a 100644
> --- a/serve.c
> +++ b/serve.c
> @@ -167,7 +167,8 @@ static int process_request(void)
>  
>  	packet_reader_init(&reader, 0, NULL, 0,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	/*
>  	 * Check to see if the client closed their end before sending another
> @@ -175,7 +176,7 @@ static int process_request(void)
>  	 */
>  	if (packet_reader_peek(&reader) == PACKET_READ_EOF)
>  		return 1;
> -	reader.options = PACKET_READ_CHOMP_NEWLINE;
> +	reader.options &= ~PACKET_READ_GENTLE_ON_EOF;

Here, the old line is meant to remove PACKET_READ_GENTLE_ON_EOF - the
new line is both necessary and clearer.

> diff --git a/t/t5703-upload-pack-ref-in-want.sh b/t/t5703-upload-pack-ref-in-want.sh
> index 3f58f05cb..d2a9d0c12 100755
> --- a/t/t5703-upload-pack-ref-in-want.sh
> +++ b/t/t5703-upload-pack-ref-in-want.sh
> @@ -208,7 +208,7 @@ test_expect_success 'server is initially ahead - no ref in want' '
>  	cp -r "$LOCAL_PRISTINE" local &&
>  	inconsistency master 1234567890123456789012345678901234567890 &&
>  	test_must_fail git -C local fetch 2>err &&
> -	grep "ERR upload-pack: not our ref" err
> +	grep "fatal: remote error: upload-pack: not our ref" err
>  '
>  
>  test_expect_success 'server is initially ahead - ref in want' '
> @@ -254,7 +254,7 @@ test_expect_success 'server loses a ref - ref in want' '
>  	echo "s/master/raster/" >"$HTTPD_ROOT_PATH/one-time-sed" &&
>  	test_must_fail git -C local fetch 2>err &&
>  
> -	grep "ERR unknown ref refs/heads/raster" err
> +	grep "fatal: remote error: unknown ref refs/heads/raster" err
>  '

And this shows that we have tests that exercise the new code.

The rest of the diff is just the addition of the new
PACKET_READ_DIE_ON_ERR_PACKET, and looks correct.

Re: [PATCH v2 1/2] Use packet_reader instead of packet_read_line

[Josh Steadmon]

On 2018.12.29 13:19, Masaya Suzuki wrote:
> By using and sharing a packet_reader while handling a Git pack protocol
> request, the same reader option is used throughout the code. This makes
> it easy to set a reader option to the request parsing code.
> 
> Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
> ---
>  builtin/archive.c      | 19 ++++++-------
>  builtin/receive-pack.c | 60 +++++++++++++++++++++--------------------
>  fetch-pack.c           | 61 +++++++++++++++++++++++-------------------
>  remote-curl.c          | 22 ++++++++++-----
>  send-pack.c            | 37 ++++++++++++-------------
>  upload-pack.c          | 38 +++++++++++++-------------
>  6 files changed, 129 insertions(+), 108 deletions(-)
> 
> diff --git a/builtin/archive.c b/builtin/archive.c
> index d2455237c..2fe1f05ca 100644
> --- a/builtin/archive.c
> +++ b/builtin/archive.c
> @@ -27,10 +27,10 @@ static int run_remote_archiver(int argc, const char **argv,
>  			       const char *remote, const char *exec,
>  			       const char *name_hint)
>  {
> -	char *buf;
>  	int fd[2], i, rv;
>  	struct transport *transport;
>  	struct remote *_remote;
> +	struct packet_reader reader;
>  
>  	_remote = remote_get(remote);
>  	if (!_remote->url[0])
> @@ -53,18 +53,19 @@ static int run_remote_archiver(int argc, const char **argv,
>  		packet_write_fmt(fd[1], "argument %s\n", argv[i]);
>  	packet_flush(fd[1]);
>  
> -	buf = packet_read_line(fd[0], NULL);
> -	if (!buf)
> +	packet_reader_init(&reader, fd[0], NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +
> +	if (packet_reader_read(&reader) != PACKET_READ_NORMAL)

packet_read_line() can also return NULL if the packet is zero-length, so
you may want to add a "|| reader.pktlen <= 0" to the condition here (and
in other places where we were checking that packet_read_line() != NULL)
to make sure the behavior doesn't change. See discussion on my previous
attempt[1] to refactor this in builtin/archive.c.

[1]: https://public-inbox.org/git/20180912053519.31085-1-steadmon@google.com/

>  		die(_("git archive: expected ACK/NAK, got a flush packet"));
> -	if (strcmp(buf, "ACK")) {
> -		if (starts_with(buf, "NACK "))
> -			die(_("git archive: NACK %s"), buf + 5);
> -		if (starts_with(buf, "ERR "))
> -			die(_("remote error: %s"), buf + 4);
> +	if (strcmp(reader.line, "ACK")) {
> +		if (starts_with(reader.line, "NACK "))
> +			die(_("git archive: NACK %s"), reader.line + 5);
> +		if (starts_with(reader.line, "ERR "))
> +			die(_("remote error: %s"), reader.line + 4);
>  		die(_("git archive: protocol error"));
>  	}
>  
> -	if (packet_read_line(fd[0], NULL))
> +	if (packet_reader_read(&reader) != PACKET_READ_FLUSH)

And here you'd want to add "&& reader.pktlen > 0". I'll skip pointing
out further instances of this issue.


>  		die(_("git archive: expected a flush"));
>  
>  	/* Now, start reading from fd[0] and spit it out to stdout */
> diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> index 33187bd8e..81cc07370 100644
> --- a/builtin/receive-pack.c
> +++ b/builtin/receive-pack.c
> @@ -1569,30 +1569,29 @@ static void queue_commands_from_cert(struct command **tail,
>  	}
>  }
>  
> -static struct command *read_head_info(struct oid_array *shallow)
> +static struct command *read_head_info(struct packet_reader *reader,
> +				      struct oid_array *shallow)
>  {
>  	struct command *commands = NULL;
>  	struct command **p = &commands;
>  	for (;;) {
> -		char *line;
> -		int len, linelen;
> +		int linelen;
>  
> -		line = packet_read_line(0, &len);
> -		if (!line)
> +		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  			break;
>  
> -		if (len > 8 && starts_with(line, "shallow ")) {
> +		if (reader->pktlen > 8 && starts_with(reader->line, "shallow ")) {
>  			struct object_id oid;
> -			if (get_oid_hex(line + 8, &oid))
> +			if (get_oid_hex(reader->line + 8, &oid))
>  				die("protocol error: expected shallow sha, got '%s'",
> -				    line + 8);
> +				    reader->line + 8);
>  			oid_array_append(shallow, &oid);
>  			continue;
>  		}
>  
> -		linelen = strlen(line);
> -		if (linelen < len) {
> -			const char *feature_list = line + linelen + 1;
> +		linelen = strlen(reader->line);
> +		if (linelen < reader->pktlen) {
> +			const char *feature_list = reader->line + linelen + 1;
>  			if (parse_feature_request(feature_list, "report-status"))
>  				report_status = 1;
>  			if (parse_feature_request(feature_list, "side-band-64k"))
> @@ -1607,28 +1606,32 @@ static struct command *read_head_info(struct oid_array *shallow)
>  				use_push_options = 1;
>  		}
>  
> -		if (!strcmp(line, "push-cert")) {
> +		if (!strcmp(reader->line, "push-cert")) {
>  			int true_flush = 0;
> -			char certbuf[1024];
> +			int saved_options = reader->options;
> +			reader->options &= ~PACKET_READ_CHOMP_NEWLINE;
>  
>  			for (;;) {
> -				len = packet_read(0, NULL, NULL,
> -						  certbuf, sizeof(certbuf), 0);
> -				if (!len) {
> +				packet_reader_read(reader);
> +				if (reader->status == PACKET_READ_FLUSH) {

Similarly, here a delim packet would previously have been caught here as
well. So it might be better to just check "reader->pktlen == 0" rather
than looking at the status. But I see in the next "if" you're adding a
new check with a die(), so I guess you're not intending to preserve the
original behavior here.


>  					true_flush = 1;
>  					break;
>  				}
> -				if (!strcmp(certbuf, "push-cert-end\n"))
> +				if (reader->status != PACKET_READ_NORMAL) {
> +					die("protocol error: got an unexpected packet");
> +				}
> +				if (!strcmp(reader->line, "push-cert-end\n"))
>  					break; /* end of cert */
> -				strbuf_addstr(&push_cert, certbuf);
> +				strbuf_addstr(&push_cert, reader->line);
>  			}
> +			reader->options = saved_options;
>  
>  			if (true_flush)
>  				break;
>  			continue;
>  		}
>  
> -		p = queue_command(p, line, linelen);
> +		p = queue_command(p, reader->line, linelen);
>  	}
>  
>  	if (push_cert.len)
> @@ -1637,18 +1640,14 @@ static struct command *read_head_info(struct oid_array *shallow)
>  	return commands;
>  }
>  
> -static void read_push_options(struct string_list *options)
> +static void read_push_options(struct packet_reader *reader,
> +			      struct string_list *options)
>  {
>  	while (1) {
> -		char *line;
> -		int len;
> -
> -		line = packet_read_line(0, &len);
> -
> -		if (!line)
> +		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  			break;
>  
> -		string_list_append(options, line);
> +		string_list_append(options, reader->line);
>  	}
>  }
>  
> @@ -1924,6 +1923,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
>  	struct oid_array shallow = OID_ARRAY_INIT;
>  	struct oid_array ref = OID_ARRAY_INIT;
>  	struct shallow_info si;
> +	struct packet_reader reader;
>  
>  	struct option options[] = {
>  		OPT__QUIET(&quiet, N_("quiet")),
> @@ -1986,12 +1986,14 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
>  	if (advertise_refs)
>  		return 0;
>  
> -	if ((commands = read_head_info(&shallow)) != NULL) {
> +	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +
> +	if ((commands = read_head_info(&reader, &shallow)) != NULL) {
>  		const char *unpack_status = NULL;
>  		struct string_list push_options = STRING_LIST_INIT_DUP;
>  
>  		if (use_push_options)
> -			read_push_options(&push_options);
> +			read_push_options(&reader, &push_options);
>  		if (!check_cert_push_options(&push_options)) {
>  			struct command *cmd;
>  			for (cmd = commands; cmd; cmd = cmd->next)
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 9691046e6..86790b9bb 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -135,38 +135,42 @@ enum ack_type {
>  	ACK_ready
>  };
>  
> -static void consume_shallow_list(struct fetch_pack_args *args, int fd)
> +static void consume_shallow_list(struct fetch_pack_args *args,
> +				 struct packet_reader *reader)
>  {
>  	if (args->stateless_rpc && args->deepen) {
>  		/* If we sent a depth we will get back "duplicate"
>  		 * shallow and unshallow commands every time there
>  		 * is a block of have lines exchanged.
>  		 */
> -		char *line;
> -		while ((line = packet_read_line(fd, NULL))) {
> -			if (starts_with(line, "shallow "))
> +		while (packet_reader_read(reader) == PACKET_READ_NORMAL) {
> +			if (starts_with(reader->line, "shallow "))
>  				continue;
> -			if (starts_with(line, "unshallow "))
> +			if (starts_with(reader->line, "unshallow "))
>  				continue;
>  			die(_("git fetch-pack: expected shallow list"));
>  		}
> +		if (reader->status != PACKET_READ_FLUSH)
> +			die(_("git fetch-pack: expected a flush packet after shallow list"));

Another behavior change here, as previously we didn't check for a final
flush packet (unless I'm missing something).


>  	}
>  }
>  
> -static enum ack_type get_ack(int fd, struct object_id *result_oid)
> +static enum ack_type get_ack(struct packet_reader *reader,
> +			     struct object_id *result_oid)
>  {
>  	int len;
> -	char *line = packet_read_line(fd, &len);
>  	const char *arg;
>  
> -	if (!line)
> +	if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  		die(_("git fetch-pack: expected ACK/NAK, got a flush packet"));
> -	if (!strcmp(line, "NAK"))
> +	len = reader->pktlen;
> +
> +	if (!strcmp(reader->line, "NAK"))
>  		return NAK;
> -	if (skip_prefix(line, "ACK ", &arg)) {
> +	if (skip_prefix(reader->line, "ACK ", &arg)) {
>  		if (!get_oid_hex(arg, result_oid)) {
>  			arg += 40;
> -			len -= arg - line;
> +			len -= arg - reader->line;
>  			if (len < 1)
>  				return ACK;
>  			if (strstr(arg, "continue"))
> @@ -178,9 +182,9 @@ static enum ack_type get_ack(int fd, struct object_id *result_oid)
>  			return ACK;
>  		}
>  	}
> -	if (skip_prefix(line, "ERR ", &arg))
> +	if (skip_prefix(reader->line, "ERR ", &arg))
>  		die(_("remote error: %s"), arg);
> -	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), line);
> +	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), reader->line);
>  }
>  
>  static void send_request(struct fetch_pack_args *args,
> @@ -248,10 +252,14 @@ static int find_common(struct fetch_negotiator *negotiator,
>  	int got_ready = 0;
>  	struct strbuf req_buf = STRBUF_INIT;
>  	size_t state_len = 0;
> +	struct packet_reader reader;
>  
>  	if (args->stateless_rpc && multi_ack == 1)
>  		die(_("--stateless-rpc requires multi_ack_detailed"));
>  
> +	packet_reader_init(&reader, fd[0], NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE);
> +
>  	if (!args->no_dependents) {
>  		mark_tips(negotiator, args->negotiation_tips);
>  		for_each_cached_alternate(negotiator, insert_one_alternate_object);
> @@ -336,31 +344,30 @@ static int find_common(struct fetch_negotiator *negotiator,
>  	state_len = req_buf.len;
>  
>  	if (args->deepen) {
> -		char *line;
>  		const char *arg;
>  		struct object_id oid;
>  
>  		send_request(args, fd[1], &req_buf);
> -		while ((line = packet_read_line(fd[0], NULL))) {
> -			if (skip_prefix(line, "shallow ", &arg)) {
> +		while (packet_reader_read(&reader) == PACKET_READ_NORMAL) {
> +			if (skip_prefix(reader.line, "shallow ", &arg)) {
>  				if (get_oid_hex(arg, &oid))
> -					die(_("invalid shallow line: %s"), line);
> +					die(_("invalid shallow line: %s"), reader.line);
>  				register_shallow(the_repository, &oid);
>  				continue;
>  			}
> -			if (skip_prefix(line, "unshallow ", &arg)) {
> +			if (skip_prefix(reader.line, "unshallow ", &arg)) {
>  				if (get_oid_hex(arg, &oid))
> -					die(_("invalid unshallow line: %s"), line);
> +					die(_("invalid unshallow line: %s"), reader.line);
>  				if (!lookup_object(the_repository, oid.hash))
> -					die(_("object not found: %s"), line);
> +					die(_("object not found: %s"), reader.line);
>  				/* make sure that it is parsed as shallow */
>  				if (!parse_object(the_repository, &oid))
> -					die(_("error in object: %s"), line);
> +					die(_("error in object: %s"), reader.line);
>  				if (unregister_shallow(&oid))
> -					die(_("no shallow found: %s"), line);
> +					die(_("no shallow found: %s"), reader.line);
>  				continue;
>  			}
> -			die(_("expected shallow/unshallow, got %s"), line);
> +			die(_("expected shallow/unshallow, got %s"), reader.line);
>  		}
>  	} else if (!args->stateless_rpc)
>  		send_request(args, fd[1], &req_buf);
> @@ -397,9 +404,9 @@ static int find_common(struct fetch_negotiator *negotiator,
>  			if (!args->stateless_rpc && count == INITIAL_FLUSH)
>  				continue;
>  
> -			consume_shallow_list(args, fd[0]);
> +			consume_shallow_list(args, &reader);
>  			do {
> -				ack = get_ack(fd[0], result_oid);
> +				ack = get_ack(&reader, result_oid);
>  				if (ack)
>  					print_verbose(args, _("got %s %d %s"), "ack",
>  						      ack, oid_to_hex(result_oid));
> @@ -469,9 +476,9 @@ static int find_common(struct fetch_negotiator *negotiator,
>  	strbuf_release(&req_buf);
>  
>  	if (!got_ready || !no_done)
> -		consume_shallow_list(args, fd[0]);
> +		consume_shallow_list(args, &reader);
>  	while (flushes || multi_ack) {
> -		int ack = get_ack(fd[0], result_oid);
> +		int ack = get_ack(&reader, result_oid);
>  		if (ack) {
>  			print_verbose(args, _("got %s (%d) %s"), "ack",
>  				      ack, oid_to_hex(result_oid));
> diff --git a/remote-curl.c b/remote-curl.c
> index 1220dffcd..bbd9ba0f3 100644
> --- a/remote-curl.c
> +++ b/remote-curl.c
> @@ -409,28 +409,36 @@ static struct discovery *discover_refs(const char *service, int for_push)
>  	if (maybe_smart &&
>  	    (5 <= last->len && last->buf[4] == '#') &&
>  	    !strbuf_cmp(&exp, &type)) {
> -		char *line;
> +		struct packet_reader reader;
> +		packet_reader_init(&reader, -1, last->buf, last->len,
> +				   PACKET_READ_CHOMP_NEWLINE);
>  
>  		/*
>  		 * smart HTTP response; validate that the service
>  		 * pkt-line matches our request.
>  		 */
> -		line = packet_read_line_buf(&last->buf, &last->len, NULL);
> -		if (!line)
> +		if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
>  			die("invalid server response; expected service, got flush packet");
>  
>  		strbuf_reset(&exp);
>  		strbuf_addf(&exp, "# service=%s", service);
> -		if (strcmp(line, exp.buf))
> -			die("invalid server response; got '%s'", line);
> +		if (strcmp(reader.line, exp.buf))
> +			die("invalid server response; got '%s'", reader.line);
>  		strbuf_release(&exp);
>  
>  		/* The header can include additional metadata lines, up
>  		 * until a packet flush marker.  Ignore these now, but
>  		 * in the future we might start to scan them.
>  		 */
> -		while (packet_read_line_buf(&last->buf, &last->len, NULL))
> -			;
> +		for (;;) {
> +			packet_reader_read(&reader);
> +			if (reader.pktlen <= 0) {
> +				break;
> +			}
> +		}
> +
> +		last->buf = reader.src_buffer;
> +		last->len = reader.src_len;
>  
>  		last->proto_git = 1;
>  	} else if (maybe_smart &&
> diff --git a/send-pack.c b/send-pack.c
> index f69268677..913645046 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -135,38 +135,36 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *extra, struc
>  	return 0;
>  }
>  
> -static int receive_unpack_status(int in)
> +static int receive_unpack_status(struct packet_reader *reader)
>  {
> -	const char *line = packet_read_line(in, NULL);
> -	if (!line)
> +	if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  		return error(_("unexpected flush packet while reading remote unpack status"));
> -	if (!skip_prefix(line, "unpack ", &line))
> -		return error(_("unable to parse remote unpack status: %s"), line);
> -	if (strcmp(line, "ok"))
> -		return error(_("remote unpack failed: %s"), line);
> +	if (!skip_prefix(reader->line, "unpack ", &reader->line))
> +		return error(_("unable to parse remote unpack status: %s"), reader->line);
> +	if (strcmp(reader->line, "ok"))
> +		return error(_("remote unpack failed: %s"), reader->line);
>  	return 0;
>  }
>  
> -static int receive_status(int in, struct ref *refs)
> +static int receive_status(struct packet_reader *reader, struct ref *refs)
>  {
>  	struct ref *hint;
>  	int ret;
>  
>  	hint = NULL;
> -	ret = receive_unpack_status(in);
> +	ret = receive_unpack_status(reader);
>  	while (1) {
> -		char *refname;
> +		const char *refname;
>  		char *msg;
> -		char *line = packet_read_line(in, NULL);
> -		if (!line)
> +		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  			break;
> -		if (!starts_with(line, "ok ") && !starts_with(line, "ng ")) {
> -			error("invalid ref status from remote: %s", line);
> +		if (!starts_with(reader->line, "ok ") && !starts_with(reader->line, "ng ")) {
> +			error("invalid ref status from remote: %s", reader->line);
>  			ret = -1;
>  			break;
>  		}
>  
> -		refname = line + 3;
> +		refname = reader->line + 3;
>  		msg = strchr(refname, ' ');
>  		if (msg)
>  			*msg++ = '\0';
> @@ -187,7 +185,7 @@ static int receive_status(int in, struct ref *refs)
>  			continue;
>  		}
>  
> -		if (line[0] == 'o' && line[1] == 'k')
> +		if (reader->line[0] == 'o' && reader->line[1] == 'k')
>  			hint->status = REF_STATUS_OK;
>  		else {
>  			hint->status = REF_STATUS_REMOTE_REJECT;
> @@ -390,6 +388,7 @@ int send_pack(struct send_pack_args *args,
>  	int ret;
>  	struct async demux;
>  	const char *push_cert_nonce = NULL;
> +	struct packet_reader reader;
>  
>  	/* Does the other end support the reporting? */
>  	if (server_supports("report-status"))
> @@ -559,6 +558,8 @@ int send_pack(struct send_pack_args *args,
>  		in = demux.out;
>  	}
>  
> +	packet_reader_init(&reader, in, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +
>  	if (need_pack_data && cmds_sent) {
>  		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
>  			for (ref = remote_refs; ref; ref = ref->next)
> @@ -573,7 +574,7 @@ int send_pack(struct send_pack_args *args,
>  			 * are failing, and just want the error() side effects.
>  			 */
>  			if (status_report)
> -				receive_unpack_status(in);
> +				receive_unpack_status(&reader);
>  
>  			if (use_sideband) {
>  				close(demux.out);
> @@ -590,7 +591,7 @@ int send_pack(struct send_pack_args *args,
>  		packet_flush(out);
>  
>  	if (status_report && cmds_sent)
> -		ret = receive_status(in, remote_refs);
> +		ret = receive_status(&reader, remote_refs);
>  	else
>  		ret = 0;
>  	if (args->stateless_rpc)
> diff --git a/upload-pack.c b/upload-pack.c
> index 5e81f1ff2..1638825ee 100644
> --- a/upload-pack.c
> +++ b/upload-pack.c
> @@ -354,7 +354,8 @@ static int ok_to_give_up(const struct object_array *have_obj,
>  					    min_generation);
>  }
>  
> -static int get_common_commits(struct object_array *have_obj,
> +static int get_common_commits(struct packet_reader *reader,
> +			      struct object_array *have_obj,
>  			      struct object_array *want_obj)
>  {
>  	struct object_id oid;
> @@ -366,12 +367,11 @@ static int get_common_commits(struct object_array *have_obj,
>  	save_commit_buffer = 0;
>  
>  	for (;;) {
> -		char *line = packet_read_line(0, NULL);
>  		const char *arg;
>  
>  		reset_timeout();
>  
> -		if (!line) {
> +		if (packet_reader_read(reader) != PACKET_READ_NORMAL) {
>  			if (multi_ack == 2 && got_common
>  			    && !got_other && ok_to_give_up(have_obj, want_obj)) {
>  				sent_ready = 1;
> @@ -390,7 +390,7 @@ static int get_common_commits(struct object_array *have_obj,
>  			got_other = 0;
>  			continue;
>  		}
> -		if (skip_prefix(line, "have ", &arg)) {
> +		if (skip_prefix(reader->line, "have ", &arg)) {
>  			switch (got_oid(arg, &oid, have_obj)) {
>  			case -1: /* they have what we do not */
>  				got_other = 1;
> @@ -416,7 +416,7 @@ static int get_common_commits(struct object_array *have_obj,
>  			}
>  			continue;
>  		}
> -		if (!strcmp(line, "done")) {
> +		if (!strcmp(reader->line, "done")) {
>  			if (have_obj->nr > 0) {
>  				if (multi_ack)
>  					packet_write_fmt(1, "ACK %s\n", last_hex);
> @@ -425,7 +425,7 @@ static int get_common_commits(struct object_array *have_obj,
>  			packet_write_fmt(1, "NAK\n");
>  			return -1;
>  		}
> -		die("git upload-pack: expected SHA1 list, got '%s'", line);
> +		die("git upload-pack: expected SHA1 list, got '%s'", reader->line);
>  	}
>  }
>  
> @@ -826,7 +826,7 @@ static int process_deepen_not(const char *line, struct string_list *deepen_not,
>  	return 0;
>  }
>  
> -static void receive_needs(struct object_array *want_obj)
> +static void receive_needs(struct packet_reader *reader, struct object_array *want_obj)
>  {
>  	struct object_array shallows = OBJECT_ARRAY_INIT;
>  	struct string_list deepen_not = STRING_LIST_INIT_DUP;
> @@ -840,33 +840,32 @@ static void receive_needs(struct object_array *want_obj)
>  		struct object *o;
>  		const char *features;
>  		struct object_id oid_buf;
> -		char *line = packet_read_line(0, NULL);
>  		const char *arg;
>  
>  		reset_timeout();
> -		if (!line)
> +		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
>  			break;
>  
> -		if (process_shallow(line, &shallows))
> +		if (process_shallow(reader->line, &shallows))
>  			continue;
> -		if (process_deepen(line, &depth))
> +		if (process_deepen(reader->line, &depth))
>  			continue;
> -		if (process_deepen_since(line, &deepen_since, &deepen_rev_list))
> +		if (process_deepen_since(reader->line, &deepen_since, &deepen_rev_list))
>  			continue;
> -		if (process_deepen_not(line, &deepen_not, &deepen_rev_list))
> +		if (process_deepen_not(reader->line, &deepen_not, &deepen_rev_list))
>  			continue;
>  
> -		if (skip_prefix(line, "filter ", &arg)) {
> +		if (skip_prefix(reader->line, "filter ", &arg)) {
>  			if (!filter_capability_requested)
>  				die("git upload-pack: filtering capability not negotiated");
>  			parse_list_objects_filter(&filter_options, arg);
>  			continue;
>  		}
>  
> -		if (!skip_prefix(line, "want ", &arg) ||
> +		if (!skip_prefix(reader->line, "want ", &arg) ||
>  		    parse_oid_hex(arg, &oid_buf, &features))
>  			die("git upload-pack: protocol error, "
> -			    "expected to get object ID, not '%s'", line);
> +			    "expected to get object ID, not '%s'", reader->line);
>  
>  		if (parse_feature_request(features, "deepen-relative"))
>  			deepen_relative = 1;
> @@ -1055,6 +1054,7 @@ void upload_pack(struct upload_pack_options *options)
>  {
>  	struct string_list symref = STRING_LIST_INIT_DUP;
>  	struct object_array want_obj = OBJECT_ARRAY_INIT;
> +	struct packet_reader reader;
>  
>  	stateless_rpc = options->stateless_rpc;
>  	timeout = options->timeout;
> @@ -1078,10 +1078,12 @@ void upload_pack(struct upload_pack_options *options)
>  	if (options->advertise_refs)
>  		return;
>  
> -	receive_needs(&want_obj);
> +	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +
> +	receive_needs(&reader, &want_obj);
>  	if (want_obj.nr) {
>  		struct object_array have_obj = OBJECT_ARRAY_INIT;
> -		get_common_commits(&have_obj, &want_obj);
> +		get_common_commits(&reader, &have_obj, &want_obj);
>  		create_pack_file(&have_obj, &want_obj);
>  	}
>  }
> -- 
> 2.20.1.415.g653613c723-goog
> 

In general I think this looks good. If you want this to be a strict
refactor with no behavior changes, you'll want to address the comments
above. Otherwise, I'd prefer if you note in the commit message where/how
the behavior is changing.

Re: [PATCH v2 2/2] pack-protocol.txt: accept error packets in any context

[Josh Steadmon]

On 2018.12.29 13:19, Masaya Suzuki wrote:
> In the Git pack protocol definition, an error packet may appear only in
> a certain context. However, servers can face a runtime error (e.g. I/O
> error) at an arbitrary timing. This patch changes the protocol to allow
> an error packet to be sent instead of any packet.
> 
> Without this protocol spec change, when a server cannot process a
> request, there's no way to tell that to a client. Since the server
> cannot produce a valid response, it would be forced to cut a connection
> without telling why. With this protocol spec change, the server can be
> more gentle in this situation. An old client may see these error packets
> as an unexpected packet, but this is not worse than having an unexpected
> EOF.
> 
> Following this protocol spec change, the error packet handling code is
> moved to pkt-line.c. Implementation wise, this implementation uses
> pkt-line to communicate with a subprocess. Since this is not a part of
> Git protocol, it's possible that a packet that is not supposed to be an
> error packet is mistakenly parsed as an error packet. This error packet
> handling is enabled only for the Git pack protocol parsing code
> considering this.
> 
> Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
> ---
>  Documentation/technical/pack-protocol.txt | 20 +++++++++++---------
>  builtin/archive.c                         |  6 +++---
>  builtin/fetch-pack.c                      |  3 ++-
>  builtin/receive-pack.c                    |  4 +++-
>  builtin/send-pack.c                       |  3 ++-
>  connect.c                                 |  3 ---
>  fetch-pack.c                              |  8 ++++----
>  pkt-line.c                                |  4 ++++
>  pkt-line.h                                |  8 ++++++--
>  remote-curl.c                             |  9 ++++++---
>  send-pack.c                               |  4 +++-
>  serve.c                                   |  5 +++--
>  t/t5703-upload-pack-ref-in-want.sh        |  4 ++--
>  transport.c                               |  3 ++-
>  upload-pack.c                             |  4 +++-
>  15 files changed, 54 insertions(+), 34 deletions(-)
> 
> diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
> index 6ac774d5f..7a2375a55 100644
> --- a/Documentation/technical/pack-protocol.txt
> +++ b/Documentation/technical/pack-protocol.txt
> @@ -22,6 +22,16 @@ protocol-common.txt. When the grammar indicate `PKT-LINE(...)`, unless
>  otherwise noted the usual pkt-line LF rules apply: the sender SHOULD
>  include a LF, but the receiver MUST NOT complain if it is not present.
>  
> +An error packet is a special pkt-line that contains an error string.
> +
> +----
> +  error-line     =  PKT-LINE("ERR" SP explanation-text)
> +----
> +
> +Throughout the protocol, where `PKT-LINE(...)` is expected, an error packet MAY
> +be sent. Once this packet is sent by a client or a server, the data transfer
> +process defined in this protocol is terminated.
> +
>  Transports
>  ----------
>  There are three transports over which the packfile protocol is
> @@ -89,13 +99,6 @@ process on the server side over the Git protocol is this:
>       "0039git-upload-pack /schacon/gitbook.git\0host=example.com\0" |
>       nc -v example.com 9418
>  
> -If the server refuses the request for some reasons, it could abort
> -gracefully with an error message.
> -
> -----
> -  error-line     =  PKT-LINE("ERR" SP explanation-text)
> -----
> -
>  
>  SSH Transport
>  -------------
> @@ -398,12 +401,11 @@ from the client).
>  Then the server will start sending its packfile data.
>  
>  ----
> -  server-response = *ack_multi ack / nak / error-line
> +  server-response = *ack_multi ack / nak
>    ack_multi       = PKT-LINE("ACK" SP obj-id ack_status)
>    ack_status      = "continue" / "common" / "ready"
>    ack             = PKT-LINE("ACK" SP obj-id)
>    nak             = PKT-LINE("NAK")
> -  error-line     =  PKT-LINE("ERR" SP explanation-text)
>  ----
>  
>  A simple clone may look like this (with no 'have' lines):
> diff --git a/builtin/archive.c b/builtin/archive.c
> index 2fe1f05ca..45d11669a 100644
> --- a/builtin/archive.c
> +++ b/builtin/archive.c
> @@ -53,15 +53,15 @@ static int run_remote_archiver(int argc, const char **argv,
>  		packet_write_fmt(fd[1], "argument %s\n", argv[i]);
>  	packet_flush(fd[1]);
>  
> -	packet_reader_init(&reader, fd[0], NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +	packet_reader_init(&reader, fd[0], NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
>  		die(_("git archive: expected ACK/NAK, got a flush packet"));
>  	if (strcmp(reader.line, "ACK")) {
>  		if (starts_with(reader.line, "NACK "))
>  			die(_("git archive: NACK %s"), reader.line + 5);
> -		if (starts_with(reader.line, "ERR "))
> -			die(_("remote error: %s"), reader.line + 4);
>  		die(_("git archive: protocol error"));
>  	}
>  
> diff --git a/builtin/fetch-pack.c b/builtin/fetch-pack.c
> index 63e69a580..85dbc2af8 100644
> --- a/builtin/fetch-pack.c
> +++ b/builtin/fetch-pack.c
> @@ -217,7 +217,8 @@ int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
>  
>  	packet_reader_init(&reader, fd[0], NULL, 0,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	switch (discover_version(&reader)) {
>  	case protocol_v2:
> diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
> index 81cc07370..d58b7750b 100644
> --- a/builtin/receive-pack.c
> +++ b/builtin/receive-pack.c
> @@ -1986,7 +1986,9 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
>  	if (advertise_refs)
>  		return 0;
>  
> -	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +	packet_reader_init(&reader, 0, NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	if ((commands = read_head_info(&reader, &shallow)) != NULL) {
>  		const char *unpack_status = NULL;
> diff --git a/builtin/send-pack.c b/builtin/send-pack.c
> index 8e3c7490f..098ebf22d 100644
> --- a/builtin/send-pack.c
> +++ b/builtin/send-pack.c
> @@ -250,7 +250,8 @@ int cmd_send_pack(int argc, const char **argv, const char *prefix)
>  
>  	packet_reader_init(&reader, fd[0], NULL, 0,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	switch (discover_version(&reader)) {
>  	case protocol_v2:
> diff --git a/connect.c b/connect.c
> index 24281b608..4813f005a 100644
> --- a/connect.c
> +++ b/connect.c
> @@ -296,7 +296,6 @@ struct ref **get_remote_heads(struct packet_reader *reader,
>  	struct ref **orig_list = list;
>  	int len = 0;
>  	enum get_remote_heads_state state = EXPECTING_FIRST_REF;
> -	const char *arg;
>  
>  	*list = NULL;
>  
> @@ -306,8 +305,6 @@ struct ref **get_remote_heads(struct packet_reader *reader,
>  			die_initial_contact(1);
>  		case PACKET_READ_NORMAL:
>  			len = reader->pktlen;
> -			if (len > 4 && skip_prefix(reader->line, "ERR ", &arg))
> -				die(_("remote error: %s"), arg);
>  			break;
>  		case PACKET_READ_FLUSH:
>  			state = EXPECTING_DONE;
> diff --git a/fetch-pack.c b/fetch-pack.c
> index 86790b9bb..3f9626dbf 100644
> --- a/fetch-pack.c
> +++ b/fetch-pack.c
> @@ -182,8 +182,6 @@ static enum ack_type get_ack(struct packet_reader *reader,
>  			return ACK;
>  		}
>  	}
> -	if (skip_prefix(reader->line, "ERR ", &arg))
> -		die(_("remote error: %s"), arg);
>  	die(_("git fetch-pack: expected ACK/NAK, got '%s'"), reader->line);
>  }
>  
> @@ -258,7 +256,8 @@ static int find_common(struct fetch_negotiator *negotiator,
>  		die(_("--stateless-rpc requires multi_ack_detailed"));
>  
>  	packet_reader_init(&reader, fd[0], NULL, 0,
> -			   PACKET_READ_CHOMP_NEWLINE);
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	if (!args->no_dependents) {
>  		mark_tips(negotiator, args->negotiation_tips);
> @@ -1358,7 +1357,8 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
>  	struct fetch_negotiator negotiator;
>  	fetch_negotiator_init(&negotiator, negotiation_algorithm);
>  	packet_reader_init(&reader, fd[0], NULL, 0,
> -			   PACKET_READ_CHOMP_NEWLINE);
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	while (state != FETCH_DONE) {
>  		switch (state) {
> diff --git a/pkt-line.c b/pkt-line.c
> index 04d10bbd0..e70ea6d88 100644
> --- a/pkt-line.c
> +++ b/pkt-line.c
> @@ -346,6 +346,10 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
>  		return PACKET_READ_EOF;
>  	}
>  
> +	if ((options & PACKET_READ_DIE_ON_ERR_PACKET) &&
> +	    starts_with(buffer, "ERR "))
> +		die(_("remote error: %s"), buffer + 4);
> +
>  	if ((options & PACKET_READ_CHOMP_NEWLINE) &&
>  	    len && buffer[len-1] == '\n')
>  		len--;
> diff --git a/pkt-line.h b/pkt-line.h
> index 5b28d4347..d7e1dbc04 100644
> --- a/pkt-line.h
> +++ b/pkt-line.h
> @@ -62,9 +62,13 @@ int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
>   *
>   * If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
>   * present) is removed from the buffer before returning.
> + *
> + * If options contains PACKET_READ_DIE_ON_ERR_PACKET, it dies when it sees an
> + * ERR packet.
>   */
> -#define PACKET_READ_GENTLE_ON_EOF (1u<<0)
> -#define PACKET_READ_CHOMP_NEWLINE (1u<<1)
> +#define PACKET_READ_GENTLE_ON_EOF     (1u<<0)
> +#define PACKET_READ_CHOMP_NEWLINE     (1u<<1)
> +#define PACKET_READ_DIE_ON_ERR_PACKET (1u<<2)
>  int packet_read(int fd, char **src_buffer, size_t *src_len, char
>  		*buffer, unsigned size, int options);
>  
> diff --git a/remote-curl.c b/remote-curl.c
> index bbd9ba0f3..10b50869c 100644
> --- a/remote-curl.c
> +++ b/remote-curl.c
> @@ -204,7 +204,8 @@ static struct ref *parse_git_refs(struct discovery *heads, int for_push)
>  
>  	packet_reader_init(&reader, -1, heads->buf, heads->len,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	heads->version = discover_version(&reader);
>  	switch (heads->version) {
> @@ -411,7 +412,8 @@ static struct discovery *discover_refs(const char *service, int for_push)
>  	    !strbuf_cmp(&exp, &type)) {
>  		struct packet_reader reader;
>  		packet_reader_init(&reader, -1, last->buf, last->len,
> -				   PACKET_READ_CHOMP_NEWLINE);
> +				   PACKET_READ_CHOMP_NEWLINE |
> +				   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  		/*
>  		 * smart HTTP response; validate that the service
> @@ -1182,7 +1184,8 @@ static void proxy_state_init(struct proxy_state *p, const char *service_name,
>  		p->headers = curl_slist_append(p->headers, buf.buf);
>  
>  	packet_reader_init(&p->reader, p->in, NULL, 0,
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	strbuf_release(&buf);
>  }
> diff --git a/send-pack.c b/send-pack.c
> index 913645046..7b9829f16 100644
> --- a/send-pack.c
> +++ b/send-pack.c
> @@ -558,7 +558,9 @@ int send_pack(struct send_pack_args *args,
>  		in = demux.out;
>  	}
>  
> -	packet_reader_init(&reader, in, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +	packet_reader_init(&reader, in, NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	if (need_pack_data && cmds_sent) {
>  		if (pack_objects(out, remote_refs, extra_have, args) < 0) {
> diff --git a/serve.c b/serve.c
> index bda085f09..317256c1a 100644
> --- a/serve.c
> +++ b/serve.c
> @@ -167,7 +167,8 @@ static int process_request(void)
>  
>  	packet_reader_init(&reader, 0, NULL, 0,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	/*
>  	 * Check to see if the client closed their end before sending another
> @@ -175,7 +176,7 @@ static int process_request(void)
>  	 */
>  	if (packet_reader_peek(&reader) == PACKET_READ_EOF)
>  		return 1;
> -	reader.options = PACKET_READ_CHOMP_NEWLINE;
> +	reader.options &= ~PACKET_READ_GENTLE_ON_EOF;
>  
>  	while (state != PROCESS_REQUEST_DONE) {
>  		switch (packet_reader_peek(&reader)) {
> diff --git a/t/t5703-upload-pack-ref-in-want.sh b/t/t5703-upload-pack-ref-in-want.sh
> index 3f58f05cb..d2a9d0c12 100755
> --- a/t/t5703-upload-pack-ref-in-want.sh
> +++ b/t/t5703-upload-pack-ref-in-want.sh
> @@ -208,7 +208,7 @@ test_expect_success 'server is initially ahead - no ref in want' '
>  	cp -r "$LOCAL_PRISTINE" local &&
>  	inconsistency master 1234567890123456789012345678901234567890 &&
>  	test_must_fail git -C local fetch 2>err &&
> -	grep "ERR upload-pack: not our ref" err
> +	grep "fatal: remote error: upload-pack: not our ref" err
>  '
>  
>  test_expect_success 'server is initially ahead - ref in want' '
> @@ -254,7 +254,7 @@ test_expect_success 'server loses a ref - ref in want' '
>  	echo "s/master/raster/" >"$HTTPD_ROOT_PATH/one-time-sed" &&
>  	test_must_fail git -C local fetch 2>err &&
>  
> -	grep "ERR unknown ref refs/heads/raster" err
> +	grep "fatal: remote error: unknown ref refs/heads/raster" err
>  '
>  
>  stop_httpd
> diff --git a/transport.c b/transport.c
> index 5a74b609f..12db4251c 100644
> --- a/transport.c
> +++ b/transport.c
> @@ -273,7 +273,8 @@ static struct ref *handshake(struct transport *transport, int for_push,
>  
>  	packet_reader_init(&reader, data->fd[0], NULL, 0,
>  			   PACKET_READ_CHOMP_NEWLINE |
> -			   PACKET_READ_GENTLE_ON_EOF);
> +			   PACKET_READ_GENTLE_ON_EOF |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	data->version = discover_version(&reader);
>  	switch (data->version) {
> diff --git a/upload-pack.c b/upload-pack.c
> index 1638825ee..08b547cf0 100644
> --- a/upload-pack.c
> +++ b/upload-pack.c
> @@ -1078,7 +1078,9 @@ void upload_pack(struct upload_pack_options *options)
>  	if (options->advertise_refs)
>  		return;
>  
> -	packet_reader_init(&reader, 0, NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> +	packet_reader_init(&reader, 0, NULL, 0,
> +			   PACKET_READ_CHOMP_NEWLINE |
> +			   PACKET_READ_DIE_ON_ERR_PACKET);
>  
>  	receive_needs(&reader, &want_obj);
>  	if (want_obj.nr) {
> -- 
> 2.20.1.415.g653613c723-goog
> 

This all looks good to me.

Reviewed-by: Josh Steadmon <steadmon@google.com>

Re: [PATCH v2 1/2] Use packet_reader instead of packet_read_line

[Masaya Suzuki]

On Mon, Jan 7, 2019 at 2:33 PM Josh Steadmon <steadmon@google.com> wrote:
>
> On 2018.12.29 13:19, Masaya Suzuki wrote:
> > By using and sharing a packet_reader while handling a Git pack protocol
> > request, the same reader option is used throughout the code. This makes
> > it easy to set a reader option to the request parsing code.
> >
> > Signed-off-by: Masaya Suzuki <masayasuzuki@google.com>
> > ---
> >  builtin/archive.c      | 19 ++++++-------
> >  builtin/receive-pack.c | 60 +++++++++++++++++++++--------------------
> >  fetch-pack.c           | 61 +++++++++++++++++++++++-------------------
> >  remote-curl.c          | 22 ++++++++++-----
> >  send-pack.c            | 37 ++++++++++++-------------
> >  upload-pack.c          | 38 +++++++++++++-------------
> >  6 files changed, 129 insertions(+), 108 deletions(-)
> >
> > diff --git a/builtin/archive.c b/builtin/archive.c
> > index d2455237c..2fe1f05ca 100644
> > --- a/builtin/archive.c
> > +++ b/builtin/archive.c
> > @@ -27,10 +27,10 @@ static int run_remote_archiver(int argc, const char **argv,
> >                              const char *remote, const char *exec,
> >                              const char *name_hint)
> >  {
> > -     char *buf;
> >       int fd[2], i, rv;
> >       struct transport *transport;
> >       struct remote *_remote;
> > +     struct packet_reader reader;
> >
> >       _remote = remote_get(remote);
> >       if (!_remote->url[0])
> > @@ -53,18 +53,19 @@ static int run_remote_archiver(int argc, const char **argv,
> >               packet_write_fmt(fd[1], "argument %s\n", argv[i]);
> >       packet_flush(fd[1]);
> >
> > -     buf = packet_read_line(fd[0], NULL);
> > -     if (!buf)
> > +     packet_reader_init(&reader, fd[0], NULL, 0, PACKET_READ_CHOMP_NEWLINE);
> > +
> > +     if (packet_reader_read(&reader) != PACKET_READ_NORMAL)
>
> packet_read_line() can also return NULL if the packet is zero-length, so
> you may want to add a "|| reader.pktlen <= 0" to the condition here (and
> in other places where we were checking that packet_read_line() != NULL)
> to make sure the behavior doesn't change. See discussion on my previous
> attempt[1] to refactor this in builtin/archive.c.
>
> [1]: https://public-inbox.org/git/20180912053519.31085-1-steadmon@google.com/

That is interesting. In Documentation/technical/protocol-common.txt,
it says "Implementations SHOULD NOT send an empty pkt-line ("0004").".
The existing code won't distinguish "0000" and "0004", while "0004" is
actually not a valid pkt-line. I'll make this patch with no behavior
change, but I think we can make that behavior change to stop accepting
0004 as 0000, and remove the pktlen checks.

Re: [PATCH v2 0/2] Accept error packets in any context

[Jonathan Nieder]

Hi,

Junio C Hamano wrote:
> Masaya Suzuki <masayasuzuki@google.com> writes:

>> This makes it possible for servers to send an error message back to clients in
>> an arbitrary situation.

Yay!  Yes, this should simplify server implementations and user support.

[...]
> In short, are you shooting js/smart-http-detect-remote-error topic
> down and replacing it with this one?
>
> As that topic is not yet in 'next', I am perfectly fine doing that.
> I just want to make sure that is what you meant, as my reading of
> [4] was a bit fuzzy.

Josh, looking at that branch, I see:

 remote-curl: die on server-side errors

	Includes a test illustrating error handling in the ref
	advertisement.  Should that be revived as a standalone patch,
	without the remote-curl.c change?

 remote-curl: tighten "version 2" check for smart-http

	A bug fix.  We had an analogous bug in the .googlesource.com
	servers and it was problematic when experimenting with
	protocol changes using placeholder version numbers YYYYmmdd
	(since that starts with a "2").

 remote-curl: refactor smart-http discovery

	A nice cleanup.

Thanks,
Jonathan

Re: [PATCH v2 0/2] Accept error packets in any context

[Jonathan Nieder]

Jonathan Nieder wrote:
> Junio C Hamano wrote:

>> In short, are you shooting js/smart-http-detect-remote-error topic
>> down and replacing it with this one?
>>
>> As that topic is not yet in 'next', I am perfectly fine doing that.
>> I just want to make sure that is what you meant, as my reading of
>> [4] was a bit fuzzy.
>
> Josh, looking at that branch, I see:
>
>  remote-curl: die on server-side errors
>
> 	Includes a test illustrating error handling in the ref
> 	advertisement.  Should that be revived as a standalone patch,
> 	without the remote-curl.c change?

In fact, it appears I have that locally:

 commit 7fe6abcd775dbffd919891d5838f8d125e41f160
 Author: Josh Steadmon <steadmon@google.com>
 Date:   Tue Dec 11 16:25:18 2018 -0800

    lib-httpd, t5551: check server-side HTTP errors

    Add an HTTP path to the test server config that returns an ERR pkt-line
    unconditionally. Verify in t5551 that remote-curl properly detects this
    ERR message and aborts.

    Signed-off-by: Josh Steadmon <steadmon@google.com>
    Signed-off-by: Jeff King <peff@peff.net>
    Signed-off-by: Junio C Hamano <gitster@pobox.com>

It's handled fine by the merge 7be333a6362882e8ffceef3de830dbbfafe99995
(Merge branch 'js/smart-http-detect-remote-error' into pu, 2019-01-11),
though.  So I think what is in "pu" is okay, without shooting any series
down.  (Alternatively we can combine them into a single five-patch
series, if the maintainer prefers.)

Thanks,
Jonathan

Re: [PATCH v2 0/2] Accept error packets in any context

[Junio C Hamano]

Jonathan Nieder <jrnieder@gmail.com> writes:

> It's handled fine by the merge 7be333a6362882e8ffceef3de830dbbfafe99995
> (Merge branch 'js/smart-http-detect-remote-error' into pu, 2019-01-11),
> though.  So I think what is in "pu" is okay, without shooting any series
> down.

Yeah, I think I wiggled that topic branch after getting a
clarification from Masaya on what is going on, so what's on 'pu'
should be in a good shape.