int main() {
int ret;
int fd_A[2];
if (pipe(fd_A) == -1) {
perror("pipe");
exit(1);
}
ret = fork();
if (ret < 0) {
perror("fork");
exit(1);
} else if (ret == 0) {
/* I am the child and I will write only, so close reading end of pipe */
// STEP 1: Add the close call below
if XXX {
perror("close");
exit(1);
}
write_to_parent(fd_A[1]);
exit(0);
}
/* I am the parent only so close writing end of pipe to child A */
// STEP 1: Add the close call below
read_from_child(fd_A[0]);
return 0;
}
G_GNUC_NORETURN static void
purple_dnsquery_resolver_run(int child_out, int child_in, gboolean show_debug)
{
dns_params_t dns_params;
const size_t zero = 0;
int rc;
#ifdef HAVE_GETADDRINFO
struct addrinfo hints, *res, *tmp;
char servname[20];
#else
struct sockaddr_in sin;
const size_t addrlen = sizeof(sin);
#endif
char *hostname;
#ifdef HAVE_SIGNAL_H
purple_restore_default_signal_handlers();
signal(SIGTRAP, trap_gdb_bug);
#endif
/*
* We resolve 1 host name for each iteration of this
* while loop.
*
* The top half of this reads in the hostname and port
* number from the socket with our parent. The bottom
* half of this resolves the IP (blocking) and sends
* the result back to our parent, when finished.
*/
while (1) {
fd_set fds;
struct timeval tv = { .tv_sec = 20, .tv_usec = 0 };
FD_ZERO(&fds);
FD_SET(child_in, &fds);
rc = select(child_in + 1, &fds, NULL, NULL, &tv);
if (!rc) {
if (show_debug)
printf("dns[%d]: nobody needs me... =(\n", getpid());
break;
}
rc = read(child_in, &dns_params, sizeof(dns_params_t));
if (rc < 0) {
fprintf(stderr, "dns[%d]: Error: Could not read dns_params: "
"%s\n", getpid(), strerror(errno));
break;
}
if (rc == 0) {
if (show_debug)
printf("dns[%d]: Oops, father has gone, wait for me, wait...!\n", getpid());
_exit(0);
}
if (dns_params.hostname[0] == '\0') {
fprintf(stderr, "dns[%d]: Error: Parent requested resolution "
"of an empty hostname (port = %d)!!!\n", getpid(),
dns_params.port);
_exit(1);
}
#ifdef USE_IDN
if (!dns_str_is_ascii(dns_params.hostname)) {
rc = purple_network_convert_idn_to_ascii(dns_params.hostname, &hostname);
if (rc != 0) {
write_to_parent(child_out, &rc, sizeof(rc));
if (show_debug)
fprintf(stderr, "dns[%d] Error: IDN conversion returned "
"%d\n", getpid(), rc);
dns_params.hostname[0] = '\0';
break;
}
} else /* intentional to execute the g_strdup */
#endif
hostname = g_strdup(dns_params.hostname);
/* We have the hostname and port, now resolve the IP */
#ifdef HAVE_GETADDRINFO
g_snprintf(servname, sizeof(servname), "%d", dns_params.port);
memset(&hints, 0, sizeof(hints));
/* This is only used to convert a service
* name to a port number. As we know we are
* passing a number already, we know this
* value will not be really used by the C
* library.
*/
hints.ai_socktype = SOCK_STREAM;
#ifdef AI_ADDRCONFIG
hints.ai_flags |= AI_ADDRCONFIG;
#endif /* AI_ADDRCONFIG */
rc = getaddrinfo(hostname, servname, &hints, &res);
write_to_parent(child_out, &rc, sizeof(rc));
if (rc != 0) {
if (show_debug)
printf("dns[%d] Error: getaddrinfo returned %d\n",
getpid(), rc);
dns_params.hostname[0] = '\0';
g_free(hostname);
hostname = NULL;
break;
}
tmp = res;
while (res) {
size_t ai_addrlen = res->ai_addrlen;
write_to_parent(child_out, &ai_addrlen, sizeof(ai_addrlen));
write_to_parent(child_out, res->ai_addr, res->ai_addrlen);
res = res->ai_next;
}
freeaddrinfo(tmp);
#else
struct hostent *hp;
if (!(hp = gethostbyname(hostname))) {
write_to_parent(child_out, &h_errno, sizeof(int));
close(child_out);
if (show_debug)
printf("DNS Error: %d\n", h_errno);
_exit(0);
}
memset(&sin, 0, sizeof(struct sockaddr_in));
memcpy(&sin.sin_addr.s_addr, hp->h_addr, hp->h_length);
sin.sin_family = hp->h_addrtype;
sin.sin_port = htons(dns_params.port);
rc = 0;
write_to_parent(child_out, &rc, sizeof(rc));
write_to_parent(child_out, &addrlen, sizeof(addrlen));
write_to_parent(child_out, &sin, addrlen);
#endif
write_to_parent(child_out, &zero, sizeof(zero));
dns_params.hostname[0] = '\0';
g_free(hostname);
hostname = NULL;
}
close(child_out);
close(child_in);
_exit(0);
}
/*
* End the DNS resolver child process functions.
*/
/*
* Begin the functions for dealing with the DNS child processes.
*/
static void
cope_with_gdb_brokenness(void)
{
#ifdef __linux__
static gboolean already_done = FALSE;
char s[256], e[512];
int n;
pid_t ppid;
if(already_done)
return;
already_done = TRUE;
ppid = getppid();
g_snprintf(s, sizeof(s), "/proc/%d/exe", ppid);
n = readlink(s, e, sizeof(e));
if(n < 0)
return;
e[MIN((gsize)n,sizeof(e)-1)] = '\0';
if(strstr(e,"gdb")) {
purple_debug_info("dns",
"Debugger detected, performing useless query...\n");
gethostbyname("x.x.x.x.x");
}
#endif
}
static void
purple_dnsquery_resolver_destroy(PurpleDnsQueryResolverProcess *resolver)
{
g_return_if_fail(resolver != NULL);
/* Keep this before the kill() call below. */
if (resolver->inpa != 0) {
purple_input_remove(resolver->inpa);
resolver->inpa = 0;
}
/*
* We might as well attempt to kill our child process. It really
* doesn't matter if this fails, because children will expire on
* their own after a few seconds.
*/
if (resolver->dns_pid > 0)
kill(resolver->dns_pid, SIGKILL);
close(resolver->fd_in);
close(resolver->fd_out);
g_free(resolver);
number_of_dns_children--;
}