libnetutils: Add synchronization per socket full operation

Take and release mutex between ifc_init() and ifc_close()
calls to prevent global ifc_ctl_sock override.

Bug: 22307208

(cherry-pick of cebcd450.)

Change-Id: Iacffd329ce2a51defa550c7e33277332045a7b9b
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>

libnetutils/dhcptool.c

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <err.h>
 #include <errno.h>
 #include <error.h>
 #include <stdbool.h>
@@ -29,12 +30,14 @@ int main(int argc, char* argv[]) {
 
   char* interface = argv[1];
   if (ifc_init()) {
-    error(EXIT_FAILURE, errno, "dhcptool %s: ifc_init failed", interface);
+    err(errno, "dhcptool %s: ifc_init failed", interface);
+    ifc_close();
+    return EXIT_FAILURE;
   }
 
   int rc = do_dhcp(interface);
   if (rc) {
-    error(0, errno, "dhcptool %s: do_dhcp failed", interface);
+    err(errno, "dhcptool %s: do_dhcp failed", interface);
   }
 
   ifc_close();

libnetutils/ifc_utils.c

@@ -19,6 +19,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <errno.h>
+#include <pthread.h>
 
 #include <sys/socket.h>
 #include <sys/select.h>
@@ -57,6 +58,8 @@
 
 static int ifc_ctl_sock = -1;
 static int ifc_ctl_sock6 = -1;
+static pthread_mutex_t ifc_sock_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+static pthread_mutex_t ifc_sock6_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 void printerr(char *fmt, ...);
 
 #define DBG 0
@@ -122,6 +125,8 @@ int string_to_ip(const char *string, struct sockaddr_storage *ss) {
 int ifc_init(void)
 {
     int ret;
+
+    pthread_mutex_lock(&ifc_sock_mutex);
     if (ifc_ctl_sock == -1) {
         ifc_ctl_sock = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
         if (ifc_ctl_sock < 0) {
@@ -136,6 +141,7 @@ int ifc_init(void)
 
 int ifc_init6(void)
 {
+    pthread_mutex_lock(&ifc_sock6_mutex);
     if (ifc_ctl_sock6 == -1) {
         ifc_ctl_sock6 = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0);
         if (ifc_ctl_sock6 < 0) {
@@ -152,6 +158,7 @@ void ifc_close(void)
         (void)close(ifc_ctl_sock);
         ifc_ctl_sock = -1;
     }
+    pthread_mutex_unlock(&ifc_sock_mutex);
 }
 
 void ifc_close6(void)
@@ -160,6 +167,7 @@ void ifc_close6(void)
         (void)close(ifc_ctl_sock6);
         ifc_ctl_sock6 = -1;
     }
+    pthread_mutex_unlock(&ifc_sock6_mutex);
 }
 
 static void ifc_init_ifr(const char *name, struct ifreq *ifr)
@@ -553,6 +561,7 @@ int ifc_act_on_ipv4_route(int action, const char *ifname, struct in_addr dst, in
     ifc_init();
 
     if (ifc_ctl_sock < 0) {
+        ifc_close();
         return -errno;
     }