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BUG/MEDIUM: http: don't disable lingering on requests with tunnelled responses

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The HTTP forwarding engine needs to disable lingering on requests in
case the connection to the server has to be suddenly closed due to
http-server-close being used, so that we don't accumulate lethal
TIME_WAIT sockets on the outgoing side. A problem happens when the
server doesn't advertise a response size, because the response
message quickly goes through the MSG_DONE and MSG_TUNNEL states,
and once the client has transferred all of its data, it turns to
MSG_DONE and immediately sets NOLINGER and closes before the server
has a chance to respond. The problem is that this destroys some of
the pending DATA being uploaded, the server doesn't receive all of
them, detects an error and closes.

This early NOLINGER is inappropriate in this situation because it
happens before the response is transmitted. This state transition
to MSG_TUNNEL doesn't happen when the response size is known since
we stay in MSG_DATA (and related states) during all the transfer.

Given that the issue is only related to connections not advertising
a response length and that by definition these connections cannot be
reused, there's no need for NOLINGER when the response's transfer
length is not known, which can be verified when entering the CLOSED
state. That's what this patch does.

This fix needs to be backported to 1.8 and very likely to 1.7 and
older as it affects the very rare case where a client immediately
closes after the last uploaded byte (typically a script). However
given that the risk of occurrence in HTTP/1 is extremely low, it is
probably wise to wait before backporting it before 1.8.
This commit is contained in:
Willy Tarreau 2017-12-14 10:43:31 +01:00
parent 13e4e94dae
commit 805935147a
1 changed files with 4 additions and 1 deletions
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5
src/proto_http.c
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@ -4523,6 +4523,10 @@ int http_sync_req_state(struct stream *s)
if (txn->req.msg_state == HTTP_MSG_CLOSED) {
http_msg_closed:
/* if we don't know whether the server will close, we need to hard close */
if (txn->rsp.flags & HTTP_MSGF_XFER_LEN)
s->si[1].flags |= SI_FL_NOLINGER; /* we want to close ASAP */
/* see above in MSG_DONE why we only do this in these states */
if (((txn->flags & TX_CON_WANT_MSK) != TX_CON_WANT_SCL) &&
((txn->flags & TX_CON_WANT_MSK) != TX_CON_WANT_KAL) &&
@ -4535,7 +4539,6 @@ int http_sync_req_state(struct stream *s)
/* Here, we are in HTTP_MSG_DONE or HTTP_MSG_TUNNEL */
if (chn->flags & (CF_SHUTW|CF_SHUTW_NOW)) {
/* if we've just closed an output, let's switch */
s->si[1].flags |= SI_FL_NOLINGER; /* we want to close ASAP */
txn->req.msg_state = HTTP_MSG_CLOSING;
goto http_msg_closing;
}