[Bug network/29717] New: getaddrinfo returns EAI_NONAME with errno set to EMFILE.

["mpoliwczak34 at gmail dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29717

            Bug ID: 29717
           Summary: getaddrinfo returns EAI_NONAME with errno set to
                    EMFILE.
           Product: glibc
           Version: 2.36
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: network
          Assignee: unassigned at sourceware dot org
          Reporter: mpoliwczak34 at gmail dot com
  Target Milestone: ---

When running out of FDs the getaddrinfo returns EAI_NONAME (instead of
EAI_SYSTEM) and it sets errno to EMFILE. The man page says that the errno is
only set it the case where getaddrinfo returns EAI_SYSTEM. I tested it also
with musl libc and it returns the correct code: EAI_SYSTEM. It seems like a bug
in glibc.

#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <fcntl.h>


int lookup_host (const char *host) {
  struct addrinfo hints, *res, *result;
  int errcode;

  memset (&hints, 0, sizeof (hints));
  hints.ai_family = PF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags |= AI_CANONNAME;

  errcode = getaddrinfo (host, NULL, &hints, &result);
  if (errcode != 0) {
        if (errcode == EAI_SYSTEM) {
                printf("eai system\n");
                perror("getaddrinfo");
      return -1;
        }
        printf("not eai system\n");
        perror("getaddrinfo");
        return -1;
   }

  freeaddrinfo(result);
  return 0;
}

int main (void) {
        for (int i = 0; i < 100; i++) {
                open("/tmp",O_WRONLY|O_TMPFILE,0640);
        }

        char* inbuf = "go.dev";
        lookup_host(inbuf);
}

Glibc:
[mateusz@arch code ]$ gcc main.c && bash -c 'ulimit -n 50 && ./a.out'
not eai system
getaddrinfo: Too many open files

Musl libc:
[mateusz@arch code ]$ musl-gcc main.c && bash -c 'ulimit -n 50 && ./a.out'
eai system
getaddrinfo: No file descriptors available

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