BUG: http: re-enable TCP quick-ack upon incomplete HTTP requests
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.
diff --git a/src/proto_http.c b/src/proto_http.c
index 87115d2..14dc24b 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -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 @@
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 @@
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 *