From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Johannes Schindelin via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, Jonathan Tan <jonathantanmy@google.com>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH] sideband: diagnose more incoming packet anomalies
Date: Tue, 27 Oct 2020 14:38:12 -0700 [thread overview]
Message-ID: <xmqqzh479wor.fsf@gitster.c.googlers.com> (raw)
In-Reply-To: <20201027204205.GA643357@coredump.intra.peff.net> (Jeff King's message of "Tue, 27 Oct 2020 16:42:05 -0400")
Jeff King <peff@peff.net> writes:
> Does this patch seem otherwise worth doing?
Yeah.
FWIW, I do not find the "dependency" thing disturbing. sideband is
an extension of the pkt-line mechansim, so it is natural that it
depends on pkt-line. I'd also be happy if enums, structures and
calls defined in both headers are made available by just including
one of them (e.g. retire sideband.h, perhaps).
> An alternate patch would be to keep the behavior the same and just
> clarify the code a bit. Something like:
This also looks OK to me from readability's point of view, but it
does not as much help the end user who is puzzled as the real thing,
I am afraid.
Thanks.
> -- >8 --
> Subject: [PATCH] demultiplex_sideband(): clarify corner cases
>
> The size checks in demultiplex_sideband() are a bit subtle and
> confusing:
>
> - we consider a zero-length packet ("0004") to be a flush packet, even
> though it's not really one. This is perhaps wrong, but it should
> never happen in our protocol, and we err on the side of history and
> leniency. We'll leave a comment indicating that we expect this case.
>
> - likewise we consider any flush-like packet (e.g., "0001" delim) to
> be a flush. I didn't confirm whether this is necessary for normal
> protocol usage. It may be for the everything-over-sideband mode
> introduced by 0bbc0bc574 ({fetch,upload}-pack: sideband v2 fetch
> response, 2019-01-16). Likewise let's leave a comment.
>
> - we check for "len < 1" to see if there's no sideband designator.
> That's confusing, because we already covered the "len == 0" case.
> What is interesting is the "len < 0" case. But that's not a missing
> sideband designator, but rather an error or EOF from the pkt-line
> code. This should never happen, though, because our callers instruct
> pkt-line to die() on EOF anyway. So let's make it more obvious
> that we're looking for a negative value here, and consider it a
> BUG() in the caller to pass us garbage.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---
> sideband.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/sideband.c b/sideband.c
> index 0a60662fa6..6ba1925614 100644
> --- a/sideband.c
> +++ b/sideband.c
> @@ -130,17 +130,18 @@ int demultiplex_sideband(const char *me, char *buf, int len,
> suffix = DUMB_SUFFIX;
> }
>
> + if (len < 0)
> + BUG("error/eof packet passed to demultiplex_sideband");
> +
> if (len == 0) {
> + /*
> + * we treat all flush-like packets (flush, delim, etc) and even
> + * empty data packets as a flush
> + */
> *sideband_type = SIDEBAND_FLUSH;
> goto cleanup;
> }
> - if (len < 1) {
> - strbuf_addf(scratch,
> - "%s%s: protocol error: no band designator",
> - scratch->len ? "\n" : "", me);
> - *sideband_type = SIDEBAND_PROTOCOL_ERROR;
> - goto cleanup;
> - }
> +
> band = buf[0] & 0xff;
> buf[len] = '\0';
> len--;
next prev parent reply other threads:[~2020-10-27 21:38 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
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 [this message]
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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