From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Jeff King <peff@peff.net>
Cc: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, Jonathan Tan <jonathantanmy@google.com>
Subject: Re: [PATCH v2 3/3] sideband: add defense against packets missing a band designator
Date: Fri, 23 Oct 2020 07:36:25 +0200 (CEST) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.2010230732250.56@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20201023084827.GE4012156@coredump.intra.peff.net>
Hi Peff,
On Fri, 23 Oct 2020, Jeff King wrote:
> On Mon, Oct 19, 2020 at 07:35:42PM +0000, Johannes Schindelin via GitGitGadget wrote:
>
> > diff --git a/pkt-line.c b/pkt-line.c
> > index 657a702927..f72048f623 100644
> > --- a/pkt-line.c
> > +++ b/pkt-line.c
> > @@ -461,8 +461,10 @@ int recv_sideband(const char *me, int in_stream, int out)
> > enum sideband_type sideband_type;
> >
> > while (1) {
> > - len = packet_read(in_stream, NULL, NULL, buf, LARGE_PACKET_MAX,
> > - 0);
> > + int status = packet_read_with_status(in_stream, NULL, NULL, buf,
> > + LARGE_PACKET_MAX, &len, 0);
> > + if (!len && status == PACKET_READ_NORMAL)
> > + BUG("missing band designator");
> > if (!demultiplex_sideband(me, buf, len, 0, &scratch,
> > &sideband_type))
>
> I also wonder if this status-check should be pushed down into
> demultiplex_sideband() by passing "status",
I tried that, but as mentioned in the commit message, fbd76cd450
(sideband: reverse its dependency on pkt-line, 2019-01-16) went out of its
way to _stop_ the code inside `demultiplex_sideband()` from relying on
anything in `pkt-line.h`. And that `PACKET_READ_NORMAL` and
`PACKET_READ_EOF` _is_ from `pkt-line.h`.
Ciao,
Dscho
> for two reasons:
>
> 1. So we don't have to repeat it (though it isn't that big)
>
> 2. The other half of this weirdness is that if we get an early EOF,
> we'll hit the "missing sideband designator" die() message. But
> that's not really what happened; we probably got a network hangup.
> And we could distinguish that case by checking for status ==
> PACKET_READ_EOF and provide a better message.
>
> Something like this (completely untested):
>
> diff --git a/sideband.c b/sideband.c
> index 0a60662fa6..6ad15ed581 100644
> --- a/sideband.c
> +++ b/sideband.c
> @@ -115,6 +115,7 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n)
> #define DUMB_SUFFIX " "
>
> int demultiplex_sideband(const char *me, char *buf, int len,
> + enum packet_read_status status,
> int die_on_error,
> struct strbuf *scratch,
> enum sideband_type *sideband_type)
> @@ -130,17 +131,29 @@ int demultiplex_sideband(const char *me, char *buf, int len,
> suffix = DUMB_SUFFIX;
> }
>
> - if (len == 0) {
> - *sideband_type = SIDEBAND_FLUSH;
> - goto cleanup;
> - }
> - if (len < 1) {
> + if (status == PACKET_READ_EOF) {
> strbuf_addf(scratch,
> - "%s%s: protocol error: no band designator",
> + "%s%s: protocol error: eof while reading packet",
> scratch->len ? "\n" : "", me);
> *sideband_type = SIDEBAND_PROTOCOL_ERROR;
> goto cleanup;
> }
> +
> + if (len < 0)
> + BUG("negative length on non-eof packet read");
> +
> + if (len == 0) {
> + if (status == PACKET_READ_NORMAL) {
> + strbuf_addf(scratch,
> + "%s%s protocol error: no band designator",
> + scratch->len ? "\n" : "", me);
> + *sideband_type = SIDEBAND_PROTOCOL_ERROR;
> + } else {
> + *sideband_type = SIDEBAND_FLUSH;
> + }
> + goto cleanup;
> + }
> +
> band = buf[0] & 0xff;
> buf[len] = '\0';
> len--;
>
next prev parent reply other threads:[~2020-10-23 12:47 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-13 14:45 [PATCH] t5500.43: make the check a bit more robust Johannes Schindelin via GitGitGadget
2020-10-13 17:53 ` Junio C Hamano
2020-10-13 18:55 ` Jeff King
2020-10-13 19:07 ` Junio C Hamano
2020-10-13 19:09 ` Jeff King
2020-10-17 3:31 ` Johannes Schindelin
2020-10-17 2:34 ` Johannes Schindelin
2020-10-19 19:35 ` [PATCH v2 0/3] Work around flakiness in t5500.43 Johannes Schindelin via GitGitGadget
2020-10-19 19:35 ` [PATCH v2 1/3] sideband: avoid reporting incomplete sideband messages Johannes Schindelin via GitGitGadget
2020-10-20 20:33 ` Junio C Hamano
2020-10-20 20:48 ` Johannes Schindelin
2020-10-20 21:33 ` Junio C Hamano
2020-10-19 19:35 ` [PATCH v2 2/3] sideband: report unhandled incomplete sideband messages as bugs Johannes Schindelin via GitGitGadget
2020-10-19 19:35 ` [PATCH v2 3/3] sideband: add defense against packets missing a band designator Johannes Schindelin via GitGitGadget
2020-10-20 20:36 ` Junio C Hamano
2020-10-23 8:34 ` Jeff King
2020-10-23 14:44 ` Junio C Hamano
2020-10-23 8:48 ` Jeff King
2020-10-23 5:36 ` Johannes Schindelin [this message]
2020-10-23 8:50 ` [PATCH v2 0/3] Work around flakiness in t5500.43 Jeff King
2020-10-26 16:04 ` Johannes Schindelin
2020-10-26 16:09 ` [PATCH v3 0/2] " Johannes Schindelin via GitGitGadget
2020-10-26 16:09 ` [PATCH v3 1/2] sideband: avoid reporting incomplete sideband messages Johannes Schindelin via GitGitGadget
2020-10-26 16:09 ` [PATCH v3 2/2] sideband: report unhandled incomplete sideband messages as bugs Johannes Schindelin via GitGitGadget
2020-10-26 18:33 ` [PATCH v3 0/2] Work around flakiness in t5500.43 Junio C Hamano
2020-10-27 6:52 ` [PATCH] sideband: diagnose more incoming packet anomalies Jeff King
2020-10-27 7:12 ` Jeff King
2020-10-27 18:56 ` Junio C Hamano
2020-10-27 20:42 ` Jeff King
2020-10-27 21:38 ` Junio C Hamano
2020-10-28 9:33 ` Jeff King
2020-10-27 7:13 ` Jeff King
2020-10-27 19:04 ` Junio C Hamano
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