bbennett-ks commented on code in PR #643:
URL: https://github.com/apache/guacamole-server/pull/643#discussion_r2981223657
##########
src/libguac/tcp.c:
##########
@@ -97,20 +97,33 @@ int guac_tcp_connect(const char* hostname, const char*
port, const int timeout)
continue;
}
- /* Structure that stores our timeout setting. */
+ /* Structure that stores our timeout setting. On Linux, select()
updates
+ timeout with the remaining time on EINTR, so no need to
reinitialize on
+ retry. */
struct timeval tv;
tv.tv_sec = timeout;
tv.tv_usec = 0;
/* Connect and wait for timeout */
if ((retval = connect(fd, current_address->ai_addr,
current_address->ai_addrlen)) < 0) {
- if (errno == EINPROGRESS) {
- /* Set up timeout. */
+ /* If connect() is in progress (EINPROGRESS) or interrupted by a
signal
+ * (EINTR), wait for the socket to become writable and check
SO_ERROR. */
+ if (errno == EINPROGRESS || errno == EINTR) {
+
+ /* Prevent overflowing fd_set. */
+ if (fd >= FD_SETSIZE) {
+ guac_error = GUAC_STATUS_INVALID_ARGUMENT;
+ guac_error_message = "File descriptor exceeds FD_SETSIZE.";
+ close(fd);
+ fd = -1;
+ continue;
+ }
+
fd_set fdset;
FD_ZERO(&fdset);
FD_SET(fd, &fdset);
-
- retval = select(fd + 1, NULL, &fdset, NULL, &tv);
+
+ GUAC_RETRY_EINTR(retval, select(fd + 1, NULL, &fdset, NULL,
&tv));
Review Comment:
I'd seen many opinions on these 2 issues so I did a deep dive into the Linux
kernel and glibc source code to be sure:
- `fd_set` is not modified if `select` returns -1.
- `struct timeval` is modified if `select()` returns -1 and `errno = EINTR`
to reflect the elapsed time. Leaving `tv` unmodified on retry means the
original timeout value is observed, even on retry.
#2 is Linux specific behavior, not behavior as defined by POSIX.
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