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[BUG] fix truncated responses with sepoll

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Due to the way Linux delivers EPOLLIN and EPOLLHUP, a closed connection
received after some server data sometimes results in truncated responses
if the client disconnects before server starts to respond. The reason
is that the EPOLLHUP flag is processed as an indication of end of
transfer while some data may remain in the system's socket buffers.

This problem could only be triggered with sepoll, although nothing should
prevent it from happening with normal epoll. In fact, the work factoring
performed by sepoll increases the risk that this bug appears.

The fix consists in making FD_POLL_HUP and FD_POLL_ERR sticky and that
they are only checked if FD_POLL_IN is not set, meaning that we have
read all pending data.

That way, the problem is definitely fixed and sepoll still remains about
17% faster than epoll since it can take into account all information
returned by the kernel.
This commit is contained in:
Willy Tarreau 2008-01-18 17:20:13 +01:00
parent b881608e57
commit d6f087ea1c
8 changed files with 50 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/proto/fd.h
View File

@ -74,9 +74,10 @@ void run_poller();
#define EV_FD_CLO(fd) (cur_poller.clo(fd))
/* recomputes the maxfd limit from the fd */
/* Prepares <fd> for being polled */
static inline void fd_insert(int fd)
{
fdtab[fd].ev = 0;
if (fd + 1 > maxfd)
maxfd = fd + 1;
}

11
include/types/fd.h
View File

@ -45,16 +45,19 @@ enum {
DIR_SIZE
};
/*
* FD_POLL_IN remains set as long as some data is pending for read.
* FD_POLL_OUT remains set as long as the fd accepts to write data.
* FD_POLL_ERR and FD_POLL_ERR remain set forever (until processed).
*/
#define FD_POLL_IN 0x01
#define FD_POLL_PRI 0x02
#define FD_POLL_OUT 0x04
#define FD_POLL_ERR 0x08
#define FD_POLL_HUP 0x10
#define FD_POLL_ANY 0x1F
#define FD_POLL_RD (FD_POLL_IN | FD_POLL_ERR | FD_POLL_HUP)
#define FD_POLL_WR (FD_POLL_OUT | FD_POLL_ERR | FD_POLL_HUP)
#define FD_POLL_DATA (FD_POLL_IN | FD_POLL_OUT)
#define FD_POLL_STICKY (FD_POLL_ERR | FD_POLL_HUP)
/* info about one given fd */
struct fdtab {

9
src/checks.c
View File

@ -240,12 +240,12 @@ static int event_srv_chk_w(int fd)
task_wakeup(t);
out_nowake:
EV_FD_CLR(fd, DIR_WR); /* nothing more to write */
fdtab[fd].ev &= ~FD_POLL_WR;
fdtab[fd].ev &= ~FD_POLL_OUT;
return 1;
out_poll:
/* The connection is still pending. We'll have to poll it
* before attempting to go further. */
fdtab[fd].ev &= ~FD_POLL_WR;
fdtab[fd].ev &= ~FD_POLL_OUT;
return 0;
out_error:
s->result |= SRV_CHK_ERROR;
@ -296,7 +296,7 @@ static int event_srv_chk_r(int fd)
#endif
if (unlikely(len < 0 && errno == EAGAIN)) {
/* we want some polling to happen first */
fdtab[fd].ev &= ~FD_POLL_RD;
fdtab[fd].ev &= ~FD_POLL_IN;
return 0;
}
@ -346,7 +346,7 @@ static int event_srv_chk_r(int fd)
EV_FD_CLR(fd, DIR_RD);
task_wakeup(t);
fdtab[fd].ev &= ~FD_POLL_RD;
fdtab[fd].ev &= ~FD_POLL_IN;
return 1;
}
@ -476,7 +476,6 @@ void process_chk(struct task *t, struct timeval *next)
fdtab[fd].peeraddr = (struct sockaddr *)&sa;
fdtab[fd].peerlen = sizeof(sa);
fdtab[fd].state = FD_STCONN; /* connection in progress */
fdtab[fd].ev = 0;
EV_FD_SET(fd, DIR_WR); /* for connect status */
#ifdef DEBUG_FULL
assert (!EV_FD_ISSET(fd, DIR_RD));

1
src/client.c
View File

@ -366,7 +366,6 @@ int event_accept(int fd) {
fdtab[cfd].cb[DIR_WR].b = s->rep;
fdtab[cfd].peeraddr = (struct sockaddr *)&s->cli_addr;
fdtab[cfd].peerlen = sizeof(s->cli_addr);
fdtab[cfd].ev = 0;
if ((p->mode == PR_MODE_HTTP && (s->flags & SN_MONITOR)) ||
(p->mode == PR_MODE_HEALTH && (p->options & PR_O_HTTP_CHK))) {

14
src/ev_sepoll.c
View File

@ -16,6 +16,7 @@
#include <common/compat.h>
#include <common/config.h>
#include <common/debug.h>
#include <common/standard.h>
#include <common/time.h>
#include <common/tools.h>
@ -285,7 +286,7 @@ REGPRM2 static void _do_poll(struct poller *p, struct timeval *exp)
* the WAIT status.
*/
fdtab[fd].ev = 0;
fdtab[fd].ev &= FD_POLL_STICKY;
if ((eo & FD_EV_MASK_R) == FD_EV_SPEC_R) {
/* The owner is interested in reading from this FD */
if (fdtab[fd].state != FD_STCLOSE && fdtab[fd].state != FD_STERROR) {
@ -412,7 +413,12 @@ REGPRM2 static void _do_poll(struct poller *p, struct timeval *exp)
/* it looks complicated but gcc can optimize it away when constants
* have same values.
*/
fdtab[fd].ev =
DPRINTF(stderr, "%s:%d: fd=%d, ev=0x%08x, e=0x%08x\n",
__FUNCTION__, __LINE__,
fd, fdtab[fd].ev, e);
fdtab[fd].ev &= FD_POLL_STICKY;
fdtab[fd].ev |=
((e & EPOLLIN ) ? FD_POLL_IN : 0) |
((e & EPOLLPRI) ? FD_POLL_PRI : 0) |
((e & EPOLLOUT) ? FD_POLL_OUT : 0) |
@ -422,14 +428,14 @@ REGPRM2 static void _do_poll(struct poller *p, struct timeval *exp)
if ((fd_list[fd].e & FD_EV_MASK_R) == FD_EV_WAIT_R) {
if (fdtab[fd].state == FD_STCLOSE || fdtab[fd].state == FD_STERROR)
continue;
if (fdtab[fd].ev & (FD_POLL_RD|FD_POLL_HUP|FD_POLL_ERR))
if (fdtab[fd].ev & (FD_POLL_IN|FD_POLL_HUP|FD_POLL_ERR))
fdtab[fd].cb[DIR_RD].f(fd);
}
if ((fd_list[fd].e & FD_EV_MASK_W) == FD_EV_WAIT_W) {
if (fdtab[fd].state == FD_STCLOSE || fdtab[fd].state == FD_STERROR)
continue;
if (fdtab[fd].ev & (FD_POLL_WR|FD_POLL_ERR))
if (fdtab[fd].ev & (FD_POLL_OUT|FD_POLL_ERR))
fdtab[fd].cb[DIR_WR].f(fd);
}
}

1
src/proto_tcp.c
View File

@ -271,7 +271,6 @@ int tcp_bind_listener(struct listener *listener, char *errmsg, int errlen)
fdtab[fd].peeraddr = NULL;
fdtab[fd].peerlen = 0;
fdtab[fd].listener = NULL;
fdtab[fd].ev = 0;
tcp_return:
if (msg && errlen)
strlcpy2(errmsg, msg, errlen);

3
src/proto_uxst.c
View File

@ -276,7 +276,6 @@ static int uxst_bind_listener(struct listener *listener)
fdtab[fd].peeraddr = NULL;
fdtab[fd].peerlen = 0;
fdtab[fd].listener = NULL;
fdtab[fd].ev = 0;
return ERR_NONE;
}
@ -499,8 +498,6 @@ int uxst_event_accept(int fd) {
fdtab[cfd].cb[DIR_WR].b = s->rep;
fdtab[cfd].peeraddr = (struct sockaddr *)&s->cli_addr;
fdtab[cfd].peerlen = sizeof(s->cli_addr);
fdtab[cfd].ev = 0;
tv_eternity(&s->req->rex);
tv_eternity(&s->req->wex);

43
src/stream_sock.c
View File

@ -21,6 +21,7 @@
#include <common/compat.h>
#include <common/config.h>
#include <common/debug.h>
#include <common/standard.h>
#include <common/time.h>
@ -41,25 +42,24 @@
* otherwise.
*/
int stream_sock_read(int fd) {
__label__ out_eternity, out_wakeup, out_error;
__label__ out_eternity, out_wakeup, out_shutdown_r, out_error;
struct buffer *b = fdtab[fd].cb[DIR_RD].b;
int ret, max, retval;
int read_poll = MAX_READ_POLL_LOOPS;
#ifdef DEBUG_FULL
fprintf(stderr,"stream_sock_read : fd=%d, owner=%p\n", fd, fdtab[fd].owner);
fprintf(stderr,"stream_sock_read : fd=%d, ev=0x%02x, owner=%p\n", fd, fdtab[fd].ev, fdtab[fd].owner);
#endif
retval = 1;
if (unlikely(fdtab[fd].ev & FD_POLL_HUP)) {
/* connection closed */
b->flags |= BF_READ_NULL;
goto out_eternity;
}
else if (unlikely(fdtab[fd].state == FD_STERROR || (fdtab[fd].ev & FD_POLL_ERR))) {
/* stop immediately on errors */
if (fdtab[fd].state == FD_STERROR || (fdtab[fd].ev & FD_POLL_ERR))
goto out_error;
}
/* stop here if we reached the end of data */
if ((fdtab[fd].ev & (FD_POLL_IN|FD_POLL_HUP)) == FD_POLL_HUP)
goto out_shutdown_r;
while (1) {
/*
@ -128,10 +128,15 @@ int stream_sock_read(int fd) {
/* if too many bytes were missing from last read, it means that
* it's pointless trying to read again because the system does
* not have them in buffers.
* not have them in buffers. BTW, if FD_POLL_HUP was present,
* it means that we have reached the end and that the connection
* is closed.
*/
if (ret < max)
if (ret < max) {
if (fdtab[fd].ev & FD_POLL_HUP)
goto out_shutdown_r;
break;
}
/* generally if we read something smaller than 1 or 2 MSS,
* it means that it's not worth trying to read again. It may
@ -147,8 +152,7 @@ int stream_sock_read(int fd) {
}
else if (ret == 0) {
/* connection closed */
b->flags |= BF_READ_NULL;
goto out_eternity;
goto out_shutdown_r;
}
else if (errno == EAGAIN) {
/* Ignore EAGAIN but inform the poller that there is
@ -180,14 +184,20 @@ int stream_sock_read(int fd) {
out_wakeup:
if (b->flags & BF_READ_STATUS)
task_wakeup(fdtab[fd].owner);
fdtab[fd].ev &= ~FD_POLL_RD;
fdtab[fd].ev &= ~FD_POLL_IN;
return retval;
out_shutdown_r:
fdtab[fd].ev &= ~FD_POLL_HUP;
b->flags |= BF_READ_NULL;
goto out_eternity;
out_error:
/* There was an error. we must wakeup the task. No need to clear
* the events, the task will do it.
*/
fdtab[fd].state = FD_STERROR;
fdtab[fd].ev &= ~FD_POLL_STICKY;
b->flags |= BF_READ_ERROR;
goto out_eternity;
}
@ -210,7 +220,7 @@ int stream_sock_write(int fd) {
#endif
retval = 1;
if (unlikely(fdtab[fd].state == FD_STERROR || (fdtab[fd].ev & FD_POLL_ERR)))
if (fdtab[fd].state == FD_STERROR || (fdtab[fd].ev & FD_POLL_ERR))
goto out_error;
while (1) {
@ -337,7 +347,7 @@ int stream_sock_write(int fd) {
out_wakeup:
if (b->flags & BF_WRITE_STATUS)
task_wakeup(fdtab[fd].owner);
fdtab[fd].ev &= ~FD_POLL_WR;
fdtab[fd].ev &= ~FD_POLL_OUT;
return retval;
out_error:
@ -345,6 +355,7 @@ int stream_sock_write(int fd) {
* the events, the task will do it.
*/
fdtab[fd].state = FD_STERROR;
fdtab[fd].ev &= ~FD_POLL_STICKY;
b->flags |= BF_WRITE_ERROR;
goto out_eternity;