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Thorough clean-up following 8270648da1.

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This commit is contained in:
Simon Kelley
2020-06-20 22:30:12 +01:00
parent 8270648da1
commit e2cb655958
1 changed files with 27 additions and 26 deletions
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53
src/dnsmasq.c
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@@ -1864,31 +1864,30 @@ static void check_dns_listeners(time_t now)
else else
{ {
int i; int i;
#ifdef HAVE_LINUX_NETWORK
/* The child process inherits the netlink socket,
which it never uses, but when the parent (us)
uses it in the future, the answer may go to the
child, resulting in the parent blocking
forever awaiting the result. To avoid this
the child closes the netlink socket, but there's
a nasty race, since the parent may use netlink
before the child has done the close.
To avoid this, the parent blocks here until a
single byte comes back up the pipe, which
is sent by the child after it has closed the
netlink socket. */
unsigned char a;
read_write(pipefd[0], &a, 1, 1);
#endif
for (i = 0; i < MAX_PROCS; i++) for (i = 0; i < MAX_PROCS; i++)
if (daemon->tcp_pids[i] == 0 && daemon->tcp_pipes[i] == -1) if (daemon->tcp_pids[i] == 0 && daemon->tcp_pipes[i] == -1)
{ {
char a;
(void)a; /* suppress potential unused warning */
daemon->tcp_pids[i] = p; daemon->tcp_pids[i] = p;
daemon->tcp_pipes[i] = pipefd[0]; daemon->tcp_pipes[i] = pipefd[0];
#ifdef HAVE_LINUX_NETWORK
/* The child process inherits the netlink socket,
which it never uses, but when the parent (us)
uses it in the future, the answer may go to the
child, resulting in the parent blocking
forever awaiting the result. To avoid this
the child closes the netlink socket, but there's
a nasty race, since the parent may use netlink
before the child has done the close.
To avoid this, the parent blocks here until a
single byte comes back up the pipe, which
is sent by the child after it has closed the
netlink socket. */
while(retry_send(read(pipefd[0], &a, 1)));
#endif
break; break;
} }
} }
@@ -1920,16 +1919,16 @@ static void check_dns_listeners(time_t now)
terminate the process. */ terminate the process. */
if (!option_bool(OPT_DEBUG)) if (!option_bool(OPT_DEBUG))
{ {
char a = 0; #ifdef HAVE_LINUX_NETWORK
(void)a; /* suppress potential unused warning */ /* See comment above re: netlink socket. */
unsigned char a = 0;
close(daemon->netlinkfd);
read_write(pipefd[1], &a, 1, 0);
#endif
alarm(CHILD_LIFETIME); alarm(CHILD_LIFETIME);
close(pipefd[0]); /* close read end in child. */ close(pipefd[0]); /* close read end in child. */
daemon->pipe_to_parent = pipefd[1]; daemon->pipe_to_parent = pipefd[1];
#ifdef HAVE_LINUX_NETWORK
/* See comment above re netlink socket. */
close(daemon->netlinkfd);
while(retry_send(write(pipefd[1], &a, 1)));
#endif
} }
/* start with no upstream connections. */ /* start with no upstream connections. */
@@ -1956,8 +1955,10 @@ static void check_dns_listeners(time_t now)
shutdown(s->tcpfd, SHUT_RDWR); shutdown(s->tcpfd, SHUT_RDWR);
close(s->tcpfd); close(s->tcpfd);
} }
if (!option_bool(OPT_DEBUG)) if (!option_bool(OPT_DEBUG))
{ {
close(daemon->pipe_to_parent);
flush_log(); flush_log();
_exit(0); _exit(0);
} }