git/sideband.c, branch v2.40.3

sideband: don't lose clear-to-eol at packet boundary

2021-06-17T05:11:36Z

When "demultiplex_sideband()" sees a nonempty message ending with CR or LF on the sideband #2, it adds "suffix" string to clear to the end of the current line, which helps when relaying a progress display whose records are terminated with CRs. But if it sees a single LF, no clear-to-end suffix should be appended, because this single LF is used to end the progress display by moving to the next line, and the final progress display above should be preserved. However, the code forgot that depending on the length of the payload line, such a CR may fall exactly at the packet boundary and the number of bytes before the CR from the beginning of the packet could be zero. In such a case, the message that was terminated by the CR were leftover in the "scratch" buffer in the previous call to the function and we still need to clear to the end of the current line. Helped-by: Junio C Hamano Helped-by: Nicolas Pitre Signed-off-by: Jiang Xin Signed-off-by: Junio C Hamano

Merge branch 'jk/sideband-more-error-checking'

2020-11-09T22:06:29Z

The code to detect premature EOF in the sideband demultiplexer has been cleaned up. * jk/sideband-more-error-checking: sideband: diagnose more sideband anomalies

Merge branch 'js/avoid-split-sideband-message'

2020-11-02T21:17:37Z

The side-band status report can be sent at the same time as the primary payload multiplexed, but the demultiplexer on the receiving end incorrectly split a single status report into two, which has been corrected. * js/avoid-split-sideband-message: test-pkt-line: drop colon from sideband identity sideband: report unhandled incomplete sideband messages as bugs sideband: avoid reporting incomplete sideband messages

sideband: diagnose more sideband anomalies

2020-10-29T16:23:29Z

In demultiplex_sideband(), there are two oddities when we check an incoming packet: - if it has zero length, then we assume it's a flush packet. This means we fail to notice the difference between a real flush and a true zero-length packet that's missing its sideband designator. It's not a huge problem in practice because we'd never send a zero-length data packet (even our keepalives are otherwise-empty sideband-1 packets). But it would be nice to detect and report the error, since it's likely to cause other confusion (we think the other side flushed, but they do not). - we try to detect packets missing their designator by checking for "if (len < 1)". But this will never trigger for "len == 0"; we've already detected that and left the function before then. It _could_ detect a negative "len" parameter. But in that case, the error message is wrong. The issue is not "no sideband" but rather "eof while reading the packet". However, this can't actually be triggered in practice, because neither of the two callers uses pkt_read's GENTLE_ON_EOF flag. Which means they'd die with "the remote end hung up unexpectedly" before we even get here. So this truly is dead code. We can improve these cases by passing in a pkt-line status to the demultiplexer, and by having recv_sideband() use GENTLE_ON_EOF. This gives us two improvements: - we can now reliably detect flush packets, and will report a normal packet missing its sideband designator as an error - we'll report an eof with a more detailed "protocol error: eof while reading sideband packet", rather than the generic "the remote end hung up unexpectedly" - when we see an eof, we'll flush the sideband scratch buffer, which may provide some hints from the remote about why they hung up (though note we already flush on newlines, so it's likely that most such messages already made it through) In some sense this patch goes against fbd76cd450 (sideband: reverse its dependency on pkt-line, 2019-01-16), which caused the sideband code not to depend on the pkt-line code. But that commit was really just trying to deal with the circular header dependency. The two modules are conceptually interlinked, and it was just trying to keep things compiling. And indeed, there's a sticking point in this patch: because pkt-line.h includes sideband.h, we can't add the reverse include we need for the sideband code to have an "enum packet_read_status" parameter. Nor can we forward declare it, because you can't forward declare an enum in C. However, C does guarantee that enums fit in an int, so we can just use that type. One alternative would be for the callers to check themselves that they got something sane from the pkt-line code. But besides duplicating logic, this gets quite tricky. Any error condition requires flushing the sideband #2 scratch buffer, which only demultiplex_sideband() knows how to do. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

sideband: avoid reporting incomplete sideband messages

2020-10-20T20:31:00Z

In 2b695ecd74d (t5500: count objects through stderr, not trace, 2020-05-06) we tried to ensure that the "Total 3" message could be grepped in Git's output, even if it sometimes got chopped up into multiple lines in the trace machinery. However, the first instance where this mattered now goes through the sideband machinery, where it is _still_ possible for messages to get chopped up: it *is* possible for the standard error stream to be sent byte-for-byte and hence it can be easily interrupted. Meaning: it is possible for the single line that we're looking for to be chopped up into multiple sideband packets, with a primary packet being delivered between them. This seems to happen occasionally in the `vs-test` part of our CI builds, i.e. with binaries built using Visual C, but not when building with GCC or clang; The symptom is that t5500.43 fails to find a line matching `remote: Total 3` in the `log` file, which ends in something along these lines: remote: Tota remote: l 3 (delta 0), reused 0 (delta 0), pack-reused 0 This should not happen, though: we have code in `demultiplex_sideband()` _specifically_ to stitch back together lines that were delivered in separate sideband packets. However, this stitching was broken in a subtle way in fbd76cd450 (sideband: reverse its dependency on pkt-line, 2019-01-16): before that change, incomplete sideband lines would not be flushed upon receiving a primary packet, but after that patch, they would be. The subtleness of this bug comes from the fact that it is easy to get confused by the ambiguous meaning of the `break` keyword: after writing the primary packet contents, the `break;` in the original version of `recv_sideband()` does _not_ break out of the `while` loop, but instead only ends the `switch` case: while (!retval) { [...] switch (band) { [...] case 1: /* Write the contents of the primary packet */ write_or_die(out, buf + 1, len); /* Here, we do *not* break out of the loop, `retval` is unchanged */ break; [...] } if (outbuf.len) { /* Write any remaining sideband messages lacking a trailing LF */ strbuf_addch(&outbuf, '\n'); xwrite(2, outbuf.buf, outbuf.len); } In contrast, after fbd76cd450 (sideband: reverse its dependency on pkt-line, 2019-01-16), the body of the `while` loop was extracted into `demultiplex_sideband()`, crucially _including_ the logic to write incomplete sideband messages: switch (band) { [...] case 1: *sideband_type = SIDEBAND_PRIMARY; /* This does not break out of the loop: the loop is in the caller */ break; [...] } cleanup: [...] /* This logic is now no longer _outside_ the loop but _inside_ */ if (scratch->len) { strbuf_addch(scratch, '\n'); xwrite(2, scratch->buf, scratch->len); } The correct way to fix this is to return from `demultiplex_sideband()` early. The caller will then write out the contents of the primary packet and continue looping. The `scratch` buffer for incomplete sideband messages is owned by that caller, and will continue to accumulate the remainder(s) of those messages. The loop will only end once `demultiplex_sideband()` returned non-zero _and_ did not indicate a primary packet, which is the case only when we hit the `cleanup:` path, in which we take care of flushing any unfinished sideband messages and release the `scratch` buffer. To ensure that this does not get broken again, we introduce a pair of subcommands of the `pkt-line` test helper that specifically chop up the sideband message and squeeze a primary packet into the middle. Final note: The other test case touched by 2b695ecd74d (t5500: count objects through stderr, not trace, 2020-05-06) is not affected by this issue because the sideband machinery is not involved there. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

sideband: mark "remote error:" prefix for translation

2020-08-07T19:01:57Z

A Git client may produce a "remote error:" message (along with whatever error the other side sent us) in two places: - when we see an ERR packet - when we're using a sideband and see sideband 3 We can't reliably translate the message the other side sent us, but we can do so for our own prefix. However, we translate only the ERR-packet case but not the sideband-3 case. Let's make them consistent (by marking both for translation). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'jt/fetch-v2-sideband'

2019-02-05T22:26:11Z

"git fetch" and "git upload-pack" learned to send all exchange over the sideband channel while talking the v2 protocol. * jt/fetch-v2-sideband: tests: define GIT_TEST_SIDEBAND_ALL {fetch,upload}-pack: sideband v2 fetch response sideband: reverse its dependency on pkt-line pkt-line: introduce struct packet_writer pack-protocol.txt: accept error packets in any context Use packet_reader instead of packet_read_line

{fetch,upload}-pack: sideband v2 fetch response

2019-01-17T19:25:07Z

Currently, a response to a fetch request has sideband support only while the packfile is being sent, meaning that the server cannot send notices until the start of the packfile. Extend sideband support in protocol v2 fetch responses to the whole response. upload-pack will advertise it if the uploadpack.allowsidebandall configuration variable is set, and fetch-pack will automatically request it if advertised. If the sideband is to be used throughout the whole response, upload-pack will use it to send errors instead of prefixing a PKT-LINE payload with "ERR ". This will be tested in a subsequent patch. Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano

sideband: reverse its dependency on pkt-line

2019-01-17T19:25:07Z

A subsequent patch will teach struct packet_reader a new field that, if set, instructs it to interpret read data as multiplexed. This will create a dependency from pkt-line to sideband. To avoid a circular dependency, split recv_sideband() into 2 parts: the reading loop (left in recv_sideband()) and the processing of the contents (in demultiplex_sideband()), and move the former into pkt-line. This reverses the direction of dependency: sideband no longer depends on pkt-line, and pkt-line now depends on sideband. Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano

sideband: color lines with keyword only

2018-12-04T03:12:46Z

When bf1a11f0a1 (sideband: highlight keywords in remote sideband output, 2018-08-07) was introduced, it was carefully considered which strings would be highlighted. However 59a255aef0 (sideband: do not read beyond the end of input, 2018-08-18) brought in a regression that the original did not test for. A line containing only the keyword and nothing else ("SUCCESS") should still be colored. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano