[PATCH] xap_helper: detect non-socket STDIN

[Eric Wong <e@80x24.org>]

We don't want to get into a worker respawn loop if somebody
just decides to start the executable from a terminal.
---
 lib/PublicInbox/XapHelper.pm | 4 ++++
 lib/PublicInbox/xap_helper.h | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/lib/PublicInbox/XapHelper.pm b/lib/PublicInbox/XapHelper.pm
index 0e79e5e2..e8eeb2dc 100644
--- a/lib/PublicInbox/XapHelper.pm
+++ b/lib/PublicInbox/XapHelper.pm
@@ -10,6 +10,7 @@ $GLP->configure(qw(require_order bundling no_ignore_case no_auto_abbrev));
 use PublicInbox::Search qw(xap_terms);
 use PublicInbox::CodeSearch;
 use PublicInbox::IPC;
+use Socket qw(SOL_SOCKET SO_TYPE SOCK_SEQPACKET AF_UNIX);
 use PublicInbox::DS qw(awaitpid);
 use POSIX qw(:signal_h);
 use Fcntl qw(LOCK_UN LOCK_EX);
@@ -254,6 +255,9 @@ sub xh_alive { $alive || scalar(keys %WORKERS) }
 
 sub start (@) {
 	my (@argv) = @_;
+	my $c = getsockopt(STDIN, SOL_SOCKET, SO_TYPE) or die "getsockopt: $!";
+	unpack('i', $c) == SOCK_SEQPACKET or die 'stdin is not SOCK_SEQPACKET';
+
 	local (%SRCH, %WORKERS);
 	local $alive = 1;
 	PublicInbox::Search::load_xapian();
diff --git a/lib/PublicInbox/xap_helper.h b/lib/PublicInbox/xap_helper.h
index a2fea266..2322d062 100644
--- a/lib/PublicInbox/xap_helper.h
+++ b/lib/PublicInbox/xap_helper.h
@@ -1108,6 +1108,12 @@ static size_t living_workers(void)
 int main(int argc, char *argv[])
 {
 	int c;
+	socklen_t slen = (socklen_t)sizeof(c);
+
+	if (getsockopt(sock_fd, SOL_SOCKET, SO_TYPE, &c, &slen))
+		err(EXIT_FAILURE, "getsockopt");
+	if (c != SOCK_SEQPACKET)
+		errx(EXIT_FAILURE, "stdin is not SOCK_SEQPACKET");
 
 	mail_nrp_init();
 	code_nrp_init();