udhcpc: properly reduce timeout if bogus packets were received

1 files changed, 16 insertions, 11 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index fb328cb03..eeef435de 100644
--- 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;
 }