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From: "nobu@ruby-lang.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug nss/26760] New: getaddrinfo_a blocks in a forked process after
 it was finished in the parent process
Date: Tue, 20 Oct 2020 13:31:47 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D26760

            Bug ID: 26760
           Summary: getaddrinfo_a blocks in a forked process after it was
                    finished in the parent process
           Product: glibc
           Version: 2.31
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: nss
          Assignee: unassigned at sourceware dot org
          Reporter: nobu@ruby-lang.org
  Target Milestone: ---

getaddrinfo_a hangs up when called in a process forked within 1 second afte=
r it
finished in the parent process.

// gaitest.c
#define _GNU_SOURCE
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>

int
test_gai(const char *where, const char *name)
{
  printf("in %s: ", where);
  fflush(stdout);
  struct gaicb req =3D {.ar_name =3D name};
  struct gaicb *reqs[1] =3D {&req};
  int ret =3D getaddrinfo_a(GAI_NOWAIT, reqs, 1, NULL);
  if (ret) goto error;
  ret =3D gai_suspend((const struct gaicb **)reqs, 1, NULL);
  if (ret) goto error;
  ret =3D gai_error(reqs[0]);
  if (ret) goto error;
  struct addrinfo *ai =3D reqs[0]->ar_result;
  if (ai) {
    printf("%s\n", ai->ai_canonname ? ai->ai_canonname : "noname");
  }
  return 0;
 error:
  fprintf(stderr, "failed: %s\n", gai_strerror(ret));
  return ret;
}

int
main(int argc, char **argv)
{
  test_gai("parent", "localhost");
  if (argc > 1) {
    printf("sleeping...");
    fflush(stdout);
    usleep((useconds_t)(atof(argv[1])*1e6));
    printf("\n");
  }
  pid_t pid =3D fork();
  if (pid =3D=3D 0) {
    test_gai("child", "localhost");
    return 0;
  }
  int status;
  waitpid(pid, &status, 0);
  return status;
}
// end of gaitest.c

$ gcc -o gaitest gaitest.c -lanl

$ ./gaitest 1
in parent: noname
sleeping...
in child: noname

$ ./gaitest 0.9
in parent: noname
sleeping...
in child: ^C

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