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krb5/krb5-1.7-io.patch
Nalin Dahyabhai 6879d98ef2 - try to avoid locking up in rsh due to client and server blocking on 
writes at the same time
2009-06-04 19:26:29 +00:00

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We can get stuck if a write is going to block because both ends are writing and
neither end is reading. This is a port of a patch which aims to solve that
problem, but for now it's incomplete because we don't handle partial writes. A
proper non-blocking implementation would require a bit more work.
diff -up krb5-1.7/src/appl/bsd/defines.h krb5-1.7/src/appl/bsd/defines.h
--- krb5-1.7/src/appl/bsd/defines.h 2008-12-15 15:29:01.000000000 -0500
+++ krb5-1.7/src/appl/bsd/defines.h 2009-06-04 14:18:48.000000000 -0400
@@ -34,6 +34,7 @@ extern int kcmd (int *sock, char **ahost
enum kcmd_proto *protonum /* input and output */
);
+extern int rcmd_stream_has_unsent_data (void);
extern int rcmd_stream_read (int fd, char *buf, size_t len, int secondary);
extern int rcmd_stream_write (int fd, char *buf, size_t len, int secondary);
extern int getport (int * /* portnum */, int * /* addrfamily */);
diff -up krb5-1.7/src/appl/bsd/kcmd.c krb5-1.7/src/appl/bsd/kcmd.c
--- krb5-1.7/src/appl/bsd/kcmd.c 2009-04-15 16:07:15.000000000 -0400
+++ krb5-1.7/src/appl/bsd/kcmd.c 2009-06-04 14:18:48.000000000 -0400
@@ -686,6 +686,11 @@ void rcmd_stream_init_normal()
output = twrite;
}
+int rcmd_stream_has_unsent_data (void)
+{
+ return (nstored > 0);
+}
+
void rcmd_stream_init_krb5(in_keyblock, encrypt_flag, lencheck, am_client,
protonum)
krb5_keyblock *in_keyblock;
@@ -846,7 +851,8 @@ static int v5_des_read(fd, buf, len, sec
cc = krb5_net_read(bsd_context, fd, &c, 1);
/* we should check for non-blocking here, but we'd have
to make it save partial reads as well. */
- if (cc <= 0) return cc; /* read error */
+ if (cc == 0) return nreturned; /* EOF */
+ if (cc < 0) return cc; /* read error */
if (cc == 1) {
if (c == 0 || !do_lencheck) break;
}
diff -up krb5-1.7/src/appl/bsd/krsh.c krb5-1.7/src/appl/bsd/krsh.c
--- krb5-1.7/src/appl/bsd/krsh.c 2009-06-04 14:18:47.000000000 -0400
+++ krb5-1.7/src/appl/bsd/krsh.c 2009-06-04 14:18:48.000000000 -0400
@@ -115,10 +115,11 @@ main(argc, argv0)
char **argv0;
{
int rem, pid = 0;
- char *host=0, **ap, buf[RCMD_BUFSIZ], *args, **argv = argv0, *user = 0;
+ char *host=0, **ap, buf[PIPE_BUF], *args, **argv = argv0, *user = 0;
register int cc;
struct passwd *pwd;
fd_set readfrom, ready;
+ fd_set writeto, ready_wr;
int one = 1;
struct servent *sp;
struct servent defaultservent;
@@ -508,9 +509,14 @@ main(argc, argv0)
FD_ZERO(&readfrom);
FD_SET(rfd2, &readfrom);
FD_SET(rem, &readfrom);
+ FD_ZERO(&writeto);
do {
+ int max_fd;
+ max_fd = (rfd2 > rem) ? rfd2 : rem;
+ max_fd = (max_fd > 2) ? max_fd : 2;
ready = readfrom;
- if (select(((rfd2 > rem) ? rfd2 : rem) + 1, &ready, 0, 0, 0) < 0) {
+ ready_wr = writeto;
+ if (select(max_fd + 1, &ready, &ready_wr, 0, 0) < 0) {
if (errno != EINTR) {
perror("select");
exit(1);
@@ -518,22 +524,38 @@ main(argc, argv0)
continue;
}
if (FD_ISSET(rfd2, &ready)) {
- errno = 0;
- cc = rcmd_stream_read(rfd2, buf, sizeof buf, 1);
- if (cc <= 0) {
- if ((errno != EWOULDBLOCK) && (errno != EAGAIN))
- FD_CLR(rfd2, &readfrom);
- } else
- (void) write(2, buf, (unsigned) cc);
+ FD_SET(2, &writeto);
+ }
+ if (FD_ISSET(2, &ready_wr)) {
+ do {
+ errno = 0;
+ cc = rcmd_stream_read(rfd2, buf, sizeof buf, 1);
+ if (cc <= 0) {
+ if ((errno != EWOULDBLOCK) && (errno != EAGAIN)) {
+ FD_CLR(rfd2, &readfrom);
+ break;
+ }
+ } else
+ (void) write(2, buf, (unsigned) cc);
+ } while (rcmd_stream_has_unsent_data());
+ FD_CLR(2, &writeto);
}
if (FD_ISSET(rem, &ready)) {
- errno = 0;
- cc = rcmd_stream_read(rem, buf, sizeof buf, 0);
- if (cc <= 0) {
- if ((errno != EWOULDBLOCK) && (errno != EAGAIN))
- FD_CLR(rem, &readfrom);
- } else
- (void) write(1, buf, (unsigned) cc);
+ FD_SET(1, &writeto);
+ }
+ if (FD_ISSET(1, &ready_wr)) {
+ do {
+ errno = 0;
+ cc = rcmd_stream_read(rem, buf, sizeof buf, 0);
+ if (cc <= 0) {
+ if ((errno != EWOULDBLOCK) && (errno != EAGAIN)) {
+ FD_CLR(rem, &readfrom);
+ break;
+ }
+ } else
+ (void) write(1, buf, (unsigned) cc);
+ } while (rcmd_stream_has_unsent_data());
+ FD_CLR(1, &writeto);
}
} while (FD_ISSET(rem, &readfrom) || FD_ISSET(rfd2, &readfrom));
if (nflag == 0)
diff -up krb5-1.7/src/appl/bsd/krshd.c krb5-1.7/src/appl/bsd/krshd.c
--- krb5-1.7/src/appl/bsd/krshd.c 2009-06-04 14:18:47.000000000 -0400
+++ krb5-1.7/src/appl/bsd/krshd.c 2009-06-04 14:18:48.000000000 -0400
@@ -583,7 +583,8 @@ void doit(f, fromp)
short port;
int pv[2], pw[2], px[2], cc;
fd_set ready, readfrom;
- char buf[RCMD_BUFSIZ], sig;
+ fd_set ready_wr, writeto;
+ char buf[PIPE_BUF], sig;
struct sockaddr_storage localaddr;
#ifdef POSIX_SIGNALS
struct sigaction sa;
@@ -1214,6 +1215,10 @@ void doit(f, fromp)
if (pw[0] > maxfd)
maxfd = pw[0];
+ if (px[1] > maxfd)
+ maxfd = px[1];
+ FD_ZERO(&writeto);
+
/* read from f, write to px[1] -- child stdin */
/* read from s, signal child */
/* read from pv[0], write to s -- child stderr */
@@ -1221,36 +1226,47 @@ void doit(f, fromp)
do {
ready = readfrom;
- if (select(maxfd + 1, &ready, (fd_set *)0,
+ ready_wr = writeto;
+ if (select(maxfd + 1, &ready, &ready_wr,
(fd_set *)0, (struct timeval *)0) < 0) {
if (errno == EINTR) {
continue;
} else {
break;
- }
+ }
}
if (port&&FD_ISSET(pv[0], &ready)) {
+ FD_SET(s, &writeto);
+ FD_CLR(pv[0], &readfrom);
+ }
+ if (port&&FD_ISSET(s, &ready_wr)) {
/* read from the child stderr, write to the net */
errno = 0;
cc = read(pv[0], buf, sizeof (buf));
- if (cc <= 0) {
+ if ((cc <= 0) ||
+ (rcmd_stream_write(s, buf, (unsigned) cc, 1) != cc)) {
shutdown(s, 1+1);
- FD_CLR(pv[0], &readfrom);
} else {
- (void) rcmd_stream_write(s, buf, (unsigned) cc, 1);
+ FD_SET(pv[0], &readfrom);
}
+ FD_CLR(s, &writeto);
}
if (FD_ISSET(pw[0], &ready)) {
+ FD_SET(f, &writeto);
+ FD_CLR(pw[0], &readfrom);
+ }
+ if (FD_ISSET(f, &ready_wr)) {
/* read from the child stdout, write to the net */
errno = 0;
cc = read(pw[0], buf, sizeof (buf));
- if (cc <= 0) {
+ if ((cc <= 0) ||
+ (rcmd_stream_write(f, buf, (unsigned) cc, 0) != cc)) {
shutdown(f, 1+1);
- FD_CLR(pw[0], &readfrom);
} else {
- (void) rcmd_stream_write(f, buf, (unsigned) cc, 0);
+ FD_SET(pw[0], &readfrom);
}
+ FD_CLR(f, &writeto);
}
if (port&&FD_ISSET(s, &ready)) {
/* read from the alternate channel, signal the child */
@@ -1268,12 +1284,15 @@ void doit(f, fromp)
}
}
if (FD_ISSET(f, &ready)) {
+ FD_SET(px[1], &writeto);
+ FD_CLR(f, &readfrom);
+ }
+ if (FD_ISSET(px[1], &ready_wr)) {
/* read from the net, write to child stdin */
errno = 0;
cc = rcmd_stream_read(f, buf, sizeof(buf), 0);
if (cc <= 0) {
(void) close(px[1]);
- FD_CLR(f, &readfrom);
} else {
int wcc;
wcc = write(px[1], buf, (unsigned) cc);
@@ -1281,17 +1300,22 @@ void doit(f, fromp)
/* pipe closed, don't read any more */
/* might check for EPIPE */
(void) close(px[1]);
- FD_CLR(f, &readfrom);
- } else if (wcc != cc) {
- syslog(LOG_INFO, "only wrote %d/%d to child",
- wcc, cc);
+ } else {
+ if (wcc != cc)
+ syslog(LOG_INFO, "only wrote %d/%d to child",
+ wcc, cc);
+ FD_SET(f, &readfrom);
}
}
+ FD_CLR(px[1], &writeto);
}
} while ((port&&FD_ISSET(s, &readfrom)) ||
FD_ISSET(f, &readfrom) ||
(port&&FD_ISSET(pv[0], &readfrom) )||
- FD_ISSET(pw[0], &readfrom));
+ FD_ISSET(pw[0], &readfrom) ||
+ (port&&FD_ISSET(s, &writeto)) ||
+ FD_ISSET(f, &writeto) ||
+ FD_ISSET(px[1], &writeto));
ignore_signals();
#ifdef KERBEROS
syslog(LOG_INFO ,
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