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Fix a pathology where a client sending ACKs for the wrong

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packet can prevent proper retransmission.
This commit is contained in:
hpa 2004-06-13 21:11:24 +00:00
parent 5fbd57b61a
commit 2cba51056f
2 changed files with 29 additions and 11 deletions
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5
CHANGES
View file

@ -1,5 +1,10 @@
$Id$ $Id$
Changes in 0.37:
Fix a pathology where a client sending ACKs for the wrong
packet can prevent proper retransmission.
Changes in 0.36: Changes in 0.36:
Portability fixes. Portability fixes.

35
tftpd/tftpd.c
View file

@ -207,25 +207,37 @@ set_socket_nonblock(int fd, int flag)
} }
/* /*
* Receive packet with synchronous timeout * Receive packet with synchronous timeout; timeout is adjusted
* to account for time spent waiting.
*/ */
static int recv_time(int s, void *rbuf, int len, unsigned int flags, static int recv_time(int s, void *rbuf, int len, unsigned int flags,
unsigned long timeout_us) unsigned long *timeout_us_p)
{ {
fd_set fdset; fd_set fdset;
struct timeval tmv; struct timeval tmv, t0, t1;
int rv, err; int rv, err;
unsigned long timeout_us = *timeout_us_p;
unsigned long timeout_left, dt;
gettimeofday(&t0, NULL);
timeout_left = timeout_us;
for ( ; ; ) { for ( ; ; ) {
FD_ZERO(&fdset); FD_ZERO(&fdset);
FD_SET(s, &fdset); FD_SET(s, &fdset);
tmv.tv_sec = timeout_us / 1000000;
tmv.tv_usec = timeout_us % 1000000;
do { do {
tmv.tv_sec = timeout_left / 1000000;
tmv.tv_usec = timeout_left % 1000000;
rv = select(s+1, &fdset, NULL, NULL, &tmv); rv = select(s+1, &fdset, NULL, NULL, &tmv);
} while ( rv == -1 && errno == EINTR ); err = errno;
gettimeofday(&t1, NULL);
dt = (t1.tv_sec - t0.tv_sec)*1000000 + (t1.tv_usec - t0.tv_usec);
*timeout_us_p = timeout_left = ( dt >= timeout_us ) ? 1 : (timeout_us - dt);
} while ( rv == -1 && err == EINTR );
if ( rv == 0 ) { if ( rv == 0 ) {
timer(0); /* Should not return */ timer(0); /* Should not return */
@ -236,6 +248,7 @@ static int recv_time(int s, void *rbuf, int len, unsigned int flags,
rv = recv(s, rbuf, len, flags); rv = recv(s, rbuf, len, flags);
err = errno; err = errno;
set_socket_nonblock(s, 0); set_socket_nonblock(s, 0);
if ( rv < 0 ) { if ( rv < 0 ) {
if ( E_WOULD_BLOCK(err) || err == EINTR ) { if ( E_WOULD_BLOCK(err) || err == EINTR ) {
continue; /* Once again, with feeling... */ continue; /* Once again, with feeling... */
@ -1178,7 +1191,7 @@ tftp_sendfile(struct formats *pf, struct tftphdr *oap, int oacklen)
goto abort; goto abort;
} }
for ( ; ; ) { for ( ; ; ) {
n = recv_time(peer, ackbuf, sizeof(ackbuf), 0, timeout); n = recv_time(peer, ackbuf, sizeof(ackbuf), 0, &timeout);
if (n < 0) { if (n < 0) {
syslog(LOG_WARNING, "tftpd: read: %m\n"); syslog(LOG_WARNING, "tftpd: read: %m\n");
goto abort; goto abort;
@ -1219,7 +1232,7 @@ tftp_sendfile(struct formats *pf, struct tftphdr *oap, int oacklen)
} }
read_ahead(file, pf->f_convert); read_ahead(file, pf->f_convert);
for ( ; ; ) { for ( ; ; ) {
n = recv_time(peer, ackbuf, sizeof (ackbuf), 0, timeout); n = recv_time(peer, ackbuf, sizeof (ackbuf), 0, &timeout);
if (n < 0) { if (n < 0) {
syslog(LOG_WARNING, "tftpd: read(ack): %m"); syslog(LOG_WARNING, "tftpd: read(ack): %m");
goto abort; goto abort;
@ -1296,7 +1309,7 @@ tftp_recvfile(struct formats *pf, struct tftphdr *oap, int oacklen)
} }
write_behind(file, pf->f_convert); write_behind(file, pf->f_convert);
for ( ; ; ) { for ( ; ; ) {
n = recv_time(peer, dp, PKTSIZE, 0, timeout); n = recv_time(peer, dp, PKTSIZE, 0, &timeout);
if (n < 0) { /* really? */ if (n < 0) { /* really? */
syslog(LOG_WARNING, "tftpd: read: %m"); syslog(LOG_WARNING, "tftpd: read: %m");
goto abort; goto abort;
@ -1331,7 +1344,7 @@ tftp_recvfile(struct formats *pf, struct tftphdr *oap, int oacklen)
(void) send(peer, ackbuf, 4, 0); (void) send(peer, ackbuf, 4, 0);
timeout_quit = 1; /* just quit on timeout */ timeout_quit = 1; /* just quit on timeout */
n = recv_time(peer, buf, sizeof (buf), 0, timeout); /* normally times out and quits */ n = recv_time(peer, buf, sizeof (buf), 0, &timeout); /* normally times out and quits */
timeout_quit = 0; timeout_quit = 0;
if (n >= 4 && /* if read some data */ if (n >= 4 && /* if read some data */