connect: On linux, enable reporting of all ICMP errors on UDP sockets

[crrodriguez]

The linux kernel does not report all ICMP errors back to userspace
due to historical reasons.
IP*_RECVERR sockopt must be turned on to have the correct behaviour
which is to pass all ICMP errors to userspace.

See
https://bugzilla.kernel.org/show_bug.cgi?id=202355<

PS: You almost certainly want this option to be set in your DNS resolver too (ares, or whatever, glibc was already fixed)

[bagder]

Are there any particular situations when this helps curl users? It seems like a good thing to me but I'm also curious since I can't recall anyone ever missing these errors in the past...

[crrodriguez]

Are there any particular situations when this helps curl users? It seems like a good thing to me but I'm also curious since I can't recall anyone ever missing these errors in the past...

When there are network errors, yes, it will help, applications will fail immediately rather than hang or wait for timeout. You have to simulate flaky network like for example what is described on the equivalent glibc bug report https://sourceware.org/bugzilla/show_bug.cgi?id=24047

[bagder]

Just some checksrc complaints:

./connect.c:1580:11: warning:  switch with space (SPACEBEFOREPAREN)
     switch (addr->family) {
           ^
./connect.c:1582:62: warning:  sizeof with space (SPACEBEFOREPAREN)
         setsockopt (*sockfd, SOL_IP, IP_RECVERR, &one, sizeof (one));
                                                              ^
./connect.c:1585:66: warning:  sizeof with space (SPACEBEFOREPAREN)
         setsockopt (*sockfd, SOL_IPV6, IPV6_RECVERR, &one, sizeof (one));
                                                                  ^

[crrodriguez]

Just some checksrc complaints:

./connect.c:1580:11: warning:  switch with space (SPACEBEFOREPAREN)
     switch (addr->family) {
           ^
./connect.c:1582:62: warning:  sizeof with space (SPACEBEFOREPAREN)
         setsockopt (*sockfd, SOL_IP, IP_RECVERR, &one, sizeof (one));
                                                              ^
./connect.c:1585:66: warning:  sizeof with space (SPACEBEFOREPAREN)
         setsockopt (*sockfd, SOL_IPV6, IPV6_RECVERR, &one, sizeof (one));
                                                                  ^

Huh.. yeah, would ned to fix that..

[crrodriguez]

That should pass..

[bagder]

It fails on macOS:

connect.c:1518:7: error: unused variable 'one' [-Werror,-Wunused-variable]
  int one = 1;
      ^
1 error generated.

[crrodriguez]

It fails on macOS:

connect.c:1518:7: error: unused variable 'one' [-Werror,-Wunused-variable]
  int one = 1;
      ^
1 error generated.

..and I can't declare it within the #if because of strict iso C..ok.. will fix that too.

[bagder]

You can move the declaration to be within the if block, right?

[crrodriguez]

You can move the declaration to be within the if block, right?

Yes, but then in other target there will be a complain that "ISO C90 forbids mixed declarations and code" and will fail too 💥

[bagder]

Why? C89/C90 says variable declarations can be in the beginning of any block (that starts with a { brace).

[crrodriguez]

Why? C89/C90 says variable declarations can be in the beginning of any block (that starts with a { brace).

Yeah, I ammended the commit now.

[bagder]

Thanks!