udhcpc: properly reduce timeout if bogus packets were received

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index fb328cb..eeef435 100644 (file)
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -343,8 +343,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
         * "continue" statements in code below jump to the top of the loop.
         */
        for (;;) {
-               tv.tv_sec = timeout;
-               tv.tv_usec = 0;
+               unsigned timestamp_before_wait;
 
                if (listen_mode != LISTEN_NONE && sockfd < 0) {
                        if (listen_mode == LISTEN_KERNEL)
@@ -354,19 +353,20 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                }
                max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
+               tv.tv_sec = timeout;
+               tv.tv_usec = 0;
                retval = 0; /* If we already timed out, fall through, else... */
                if (tv.tv_sec > 0) {
+                       timestamp_before_wait = (unsigned)monotonic_sec();
                        DEBUG("Waiting on select...");
                        retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
-               }
-
-               if (retval < 0) {
-                       /* EINTR? signal was caught, don't panic */
-                       if (errno != EINTR) {
+                       if (retval < 0) {
+                               /* EINTR? A signal was caught, don't panic */
+                               if (errno == EINTR)
+                                       continue;
                                /* Else: an error occured, panic! */
                                bb_perror_msg_and_die("select");
                        }
-                       continue;
                }
 
                /* If timeout dropped to zero, time to become active:
@@ -431,7 +431,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                        /* send a request packet */
                                        send_renew(xid, server_addr, requested_ip); /* unicast */
                                        t1 += (t2 - t1) / 2;
-                                       timeout = t1 - ((int)monotonic_sec() - timestamp_got_lease);
+                                       timeout = t1 - ((unsigned)monotonic_sec() - timestamp_got_lease);
                                        continue;
                                }
                                /* Timed out, enter rebinding state */
@@ -446,7 +446,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                                        /* send a request packet */
                                        send_renew(xid, 0, requested_ip); /* broadcast */
                                        t2 += (lease_seconds - t2) / 2;
-                                       timeout = t2 - ((int)monotonic_sec() - timestamp_got_lease);
+                                       timeout = t2 - ((unsigned)monotonic_sec() - timestamp_got_lease);
                                        continue;
                                }
                                /* Timed out, enter init state */
@@ -474,6 +474,11 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
                        else
                                len = get_raw_packet(&packet, sockfd);
 
+                       /* If this packet will turn out to be unrelated/bogus,
+                        * we will go back and wait for next one.
+                        * Be sure timeout is properly decreased. */
+                       timeout -= (unsigned)monotonic_sec() - timestamp_before_wait;
+
                        if (len == -1) { /* error is severe, reopen socket */
                                DEBUG("error on read, %s, reopening socket", strerror(errno));
                                change_listen_mode(listen_mode); /* just close and reopen */
@@ -628,7 +633,7 @@ int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
  ret0:
        retval = 0;
  ret:
-       /*if (client_config.pidfile) - remove_pidfile has it's own check */
+       /*if (client_config.pidfile) - remove_pidfile has its own check */
                remove_pidfile(client_config.pidfile);
        return retval;
 }