bbennett-ks opened a new pull request, #644:
URL: https://github.com/apache/guacamole-server/pull/644
## Summary
This PR hardens guac_wait_for_fd() against signal interruption (EINTR). This
is a subset of GUACAMOLE-2238.
When a signal is delivered (e.g. when a child process exits), some blocking
syscalls can return early with -1 with **errno = EINTR** . This is not a hard
failure: the syscall should be retried.
This PR adds EINTR retry loops around blocking calls in various
guacamole-server. Equivalent handling for the Windows equivalent was also added.
Without retry, signal (async) delivery can cause **guac_wait_for_fd()** to
intermittently fail.
# select Handling
` int select(int nfds, fd_set *_Nullable restrict readfds,
fd_set *_Nullable restrict writefds,
fd_set *_Nullable restrict exceptfds,
struct timeval *_Nullable restrict timeout);
`
Special care has been taken with the **select** system call, as it has
parameters which are modified by the system: how these parameters are handled
on retry must be considered. Based on the Linux man page:
`On error, -1 is returned, and is set to indicate the error;
the file descriptor sets are unmodified, and timeout becomes
undefined.`
**select** retry is based on this.
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