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BUG: http: re-enable TCP quick-ack upon incomplete HTTP requests

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By default we disable TCP quick-acking on HTTP requests so that we
avoid sending a pure ACK immediately followed by the HTTP response.
However, if the client sends an incomplete request in a short packet,
its TCP stack might wait for this packet to be ACKed before sending
the rest of the request, delaying incoming requests by up to 40-200ms.

We can detect this undesirable situation when parsing the request :
  - if an incomplete request is received
  - if a full request is received and uses chunked encoding or advertises
    a content-length larger than the data available in the buffer

In these situations, we re-enable TCP quick-ack if we had previously
disabled it.
This commit is contained in:
Willy Tarreau 2011-12-17 16:34:27 +01:00
parent b6672b547a
commit 5e205524ad
1 changed files with 24 additions and 1 deletions
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25
src/proto_http.c
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@ -19,6 +19,8 @@
#include <syslog.h>
#include <time.h>
#include <netinet/tcp.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
@ -2582,6 +2584,15 @@ int http_wait_for_request(struct session *s, struct buffer *req, int an_bit)
buffer_dont_connect(req);
req->flags |= BF_READ_DONTWAIT; /* try to get back here ASAP */
s->rep->flags &= ~BF_EXPECT_MORE; /* speed up sending a previous response */
#ifdef TCP_QUICKACK
if (s->listener->options & LI_O_NOQUICKACK) {
/* We need more data, we have to re-enable quick-ack in case we
* previously disabled it, otherwise we might cause the client
* to delay next data.
*/
setsockopt(s->si[0].fd, IPPROTO_TCP, TCP_QUICKACK, &one, sizeof(one));
}
#endif
if ((msg->msg_state != HTTP_MSG_RQBEFORE) && (txn->flags & TX_WAIT_NEXT_RQ)) {
/* If the client starts to talk, let's fall back to
@ -3692,8 +3703,20 @@ int http_process_request(struct session *s, struct buffer *req, int an_bit)
req->analysers |= AN_REQ_HTTP_BODY;
}
if (txn->flags & TX_REQ_XFER_LEN)
if (txn->flags & TX_REQ_XFER_LEN) {
req->analysers |= AN_REQ_HTTP_XFER_BODY;
#ifdef TCP_QUICKACK
/* We expect some data from the client. Unless we know for sure
* we already have a full request, we have to re-enable quick-ack
* in case we previously disabled it, otherwise we might cause
* the client to delay further data.
*/
if ((s->listener->options & LI_O_NOQUICKACK) &&
((txn->flags & TX_REQ_TE_CHNK) ||
(msg->body_len > req->l - txn->req.eoh - 2)))
setsockopt(s->si[0].fd, IPPROTO_TCP, TCP_QUICKACK, &one, sizeof(one));
#endif
}
/*************************************************************
* OK, that's finished for the headers. We have done what we *