dhcpc: cleanup and comments; fix buggy timeout handling in corner cases.

-25 bytes.

1 files changed, 125 insertions, 107 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index b3b89459e..234ecfd13 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -24,7 +24,7 @@
  * in the code. Manpage says that struct in_addr has a member of type long (!)
  * which holds IPv4 address, and the struct is passed by value (!!)
  */
-static unsigned timeout;
+static int timeout; /* = 0. Must be signed */
 static uint32_t requested_ip; /* = 0 */
 static uint32_t server_addr;
 static int packet_num; /* = 0 */
@@ -41,7 +41,7 @@ static smallint state;
 
 
 /* just a little helper */
-static void change_mode(int new_mode)
+static void change_listen_mode(int new_mode)
 {
         DEBUG("entering %s listen mode",
                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
@@ -59,7 +59,7 @@ static void perform_renew(void)
         bb_info_msg("Performing a DHCP renew");
         switch (state) {
         case BOUND:
-                change_mode(LISTEN_KERNEL);
+                change_listen_mode(LISTEN_KERNEL);
         case RENEWING:
         case REBINDING:
                 state = RENEW_REQUESTED;
@@ -68,7 +68,7 @@ static void perform_renew(void)
                 udhcp_run_script(NULL, "deconfig");
         case REQUESTING:
         case RELEASED:
-                change_mode(LISTEN_RAW);
+                change_listen_mode(LISTEN_RAW);
                 state = INIT_SELECTING;
                 break;
         case INIT_SELECTING:
@@ -101,7 +101,7 @@ static void perform_release(void)
         }
         bb_info_msg("Entering released state");
 
-        change_mode(LISTEN_NONE);
+        change_listen_mode(LISTEN_NONE);
         state = RELEASED;
         timeout = INT_MAX;
 }
@@ -153,10 +153,9 @@ int udhcpc_main(int argc, char **argv)
         char *str_W;
 #endif
         uint32_t xid = 0;
-        uint32_t lease = 0; /* can be given as 32-bit quantity */
+        uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
         unsigned t1 = 0, t2 = 0; /* what a wonderful names */
-        unsigned start = 0;
-        unsigned now;
+        unsigned timestamp_got_lease = 0; /* for gcc */
         unsigned opt;
         int max_fd;
         int retval;
@@ -324,13 +323,14 @@ int udhcpc_main(int argc, char **argv)
 
         state = INIT_SELECTING;
         udhcp_run_script(NULL, "deconfig");
-        change_mode(LISTEN_RAW);
-        tv.tv_sec = 0;
-        goto jump_in;
+        change_listen_mode(LISTEN_RAW);
 
+        /* Main event loop. select() waits on signal pipe and possibly
+         * on sockfd.
+         * "continue" statements in code below jump to the top of the loop.
+         */
         for (;;) {
-                tv.tv_sec = timeout - monotonic_sec();
- jump_in:
+                tv.tv_sec = timeout;
                 tv.tv_usec = 0;
 
                 if (listen_mode != LISTEN_NONE && sockfd < 0) {
@@ -347,15 +347,19 @@ int udhcpc_main(int argc, char **argv)
                         retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
                 }
 
-                now = monotonic_sec();
                 if (retval < 0) {
                         /* EINTR? signal was caught, don't panic */
                         if (errno != EINTR) {
                                 /* Else: an error occured, panic! */
                                 bb_perror_msg_and_die("select");
                         }
-                } else if (retval == 0) {
-                        /* timeout dropped to zero */
+                        continue;
+                }
+
+                /* If timeout dropped to zero, time to become active:
+                 * resend discover/renew/whatever
+                 */
+                if (retval == 0) {
                         switch (state) {
                         case INIT_SELECTING:
                                 if (packet_num < discover_retries) {
@@ -365,23 +369,23 @@ int udhcpc_main(int argc, char **argv)
                                         /* send discover packet */
                                         send_discover(xid, requested_ip); /* broadcast */
 
-                                        timeout = now + discover_timeout;
+                                        timeout = discover_timeout;
                                         packet_num++;
-                                } else {
-                                        udhcp_run_script(NULL, "leasefail");
-                                        if (client_config.background_if_no_lease) {
-                                                bb_info_msg("No lease, forking to background");
-                                                client_background();
-                                        } else if (client_config.abort_if_no_lease) {
-                                                bb_info_msg("No lease, failing");
-                                                retval = 1;
-                                                goto ret;
-                                        }
-                                        /* wait to try again */
-                                        packet_num = 0;
-                                        timeout = now + tryagain_timeout;
+                                        continue;
                                 }
-                                break;
+                                udhcp_run_script(NULL, "leasefail");
+                                if (client_config.background_if_no_lease) {
+                                        bb_info_msg("No lease, forking to background");
+                                        client_background();
+                                } else if (client_config.abort_if_no_lease) {
+                                        bb_info_msg("No lease, failing");
+                                        retval = 1;
+                                        goto ret;
+                                }
+                                /* wait to try again */
+                                timeout = tryagain_timeout;
+                                packet_num = 0;
+                                continue;
                         case RENEW_REQUESTED:
                         case REQUESTING:
                                 if (packet_num < discover_retries) {
@@ -390,62 +394,67 @@ int udhcpc_main(int argc, char **argv)
                                                 send_renew(xid, server_addr, requested_ip); /* unicast */
                                         else send_selecting(xid, server_addr, requested_ip); /* broadcast */
 
-                                        timeout = now + ((packet_num == 2) ? 10 : 2);
+                                        timeout = ((packet_num == 2) ? 10 : 2);
                                         packet_num++;
-                                } else {
-                                        /* timed out, go back to init state */
-                                        if (state == RENEW_REQUESTED)
-                                                udhcp_run_script(NULL, "deconfig");
-                                        state = INIT_SELECTING;
-                                        timeout = now;
-                                        packet_num = 0;
-                                        change_mode(LISTEN_RAW);
+                                        continue;
                                 }
-                                break;
+                                /* timed out, go back to init state */
+                                if (state == RENEW_REQUESTED)
+                                        udhcp_run_script(NULL, "deconfig");
+                                change_listen_mode(LISTEN_RAW);
+                                state = INIT_SELECTING;
+                                timeout = 0;
+                                packet_num = 0;
+                                continue;
                         case BOUND:
                                 /* Lease is starting to run out, time to enter renewing state */
-                                state = RENEWING;
-                                change_mode(LISTEN_KERNEL);
+                                change_listen_mode(LISTEN_KERNEL);
                                 DEBUG("Entering renew state");
+                                state = RENEWING;
                                 /* fall right through */
                         case RENEWING:
                                 /* Either set a new T1, or enter REBINDING state */
-                                if ((t2 - t1) <= (lease / 14400 + 1)) {
-                                        /* timed out, enter rebinding state */
-                                        state = REBINDING;
-                                        timeout = now + (t2 - t1);
-                                        DEBUG("Entering rebinding state");
-                                } else {
+                                if ((t2 - t1) > (lease_seconds / (4*60*60) + 1)) {
                                         /* send a request packet */
                                         send_renew(xid, server_addr, requested_ip); /* unicast */
-                                        t1 = (t2 - t1) / 2 + t1;
-                                        timeout = start + t1;
+                                        t1 += (t2 - t1) / 2;
+                                        timeout = t1 - ((int)monotonic_sec() - timestamp_got_lease);
+                                        continue;
                                 }
-                                break;
+                                /* Timed out, enter rebinding state */
+                                DEBUG("Entering rebinding state");
+                                state = REBINDING;
+                                timeout = (t2 - t1);
+                                continue;
                         case REBINDING:
-                                /* Either set a new T2, or enter INIT state */
-                                if ((lease - t2) <= (lease / 14400 + 1)) {
-                                        /* timed out, enter init state */
-                                        state = INIT_SELECTING;
-                                        bb_info_msg("Lease lost, entering init state");
-                                        udhcp_run_script(NULL, "deconfig");
-                                        timeout = now;
-                                        packet_num = 0;
-                                        change_mode(LISTEN_RAW);
-                                } else {
+                                /* Lease is *really* about to run out,
+                                 * try to find DHCP server using broadcast */
+                                if ((lease_seconds - t2) > (lease_seconds / (4*60*60) + 1)) {
                                         /* send a request packet */
                                         send_renew(xid, 0, requested_ip); /* broadcast */
-                                        t2 = (lease - t2) / 2 + t2;
-                                        timeout = start + t2;
+                                        t2 += (lease_seconds - t2) / 2;
+                                        timeout = t2 - ((int)monotonic_sec() - timestamp_got_lease);
+                                        continue;
                                 }
-                                break;
-                        case RELEASED:
-                                /* yah, I know, *you* say it would never happen */
-                                timeout = INT_MAX;
-                                break;
+                                /* Timed out, enter init state */
+                                bb_info_msg("Lease lost, entering init state");
+                                udhcp_run_script(NULL, "deconfig");
+                                change_listen_mode(LISTEN_RAW);
+                                state = INIT_SELECTING;
+                                timeout = 0;
+                                packet_num = 0;
+                                continue;
+                        /* case RELEASED: */
                         }
-                } else if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
-                        /* a packet is ready, read it */
+                        /* yah, I know, *you* say it would never happen */
+                        timeout = INT_MAX;
+                        continue; /* back to main loop */
+                }
+
+                /* select() didn't timeout, something did happen. */
+                /* Is is a packet? */
+                if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
+                        /* A packet is ready, read it */
 
                         if (listen_mode == LISTEN_KERNEL)
                                 len = udhcp_get_packet(&packet, sockfd);
@@ -453,7 +462,7 @@ int udhcpc_main(int argc, char **argv)
 
                         if (len == -1 && errno != EINTR) {
                                 DEBUG("error on read, %s, reopening socket", strerror(errno));
-                                change_mode(listen_mode); /* just close and reopen */
+                                change_listen_mode(listen_mode); /* just close and reopen */
                         }
                         if (len < 0) continue;
 
@@ -471,7 +480,7 @@ int udhcpc_main(int argc, char **argv)
 
                         message = get_option(&packet, DHCP_MESSAGE_TYPE);
                         if (message == NULL) {
-                                bb_error_msg("cannot get option from packet - ignoring");
+                                bb_error_msg("cannot get message type from packet - ignoring");
                                 continue;
                         }
 
@@ -479,22 +488,24 @@ int udhcpc_main(int argc, char **argv)
                         case INIT_SELECTING:
                                 /* Must be a DHCPOFFER to one of our xid's */
                                 if (*message == DHCPOFFER) {
+                        /* TODO: why we don't just fetch server's IP from IP header? */
                                         temp = get_option(&packet, DHCP_SERVER_ID);
-                                        if (temp) {
-                                                /* can be misaligned, thus memcpy */
-                                                memcpy(&server_addr, temp, 4);
-                                                xid = packet.xid;
-                                                requested_ip = packet.yiaddr;
-
-                                                /* enter requesting state */
-                                                state = REQUESTING;
-                                                timeout = now;
-                                                packet_num = 0;
-                                        } else {
+                                        if (!temp) {
                                                 bb_error_msg("no server ID in message");
+                                                continue;
+                                                /* still selecting - this server looks bad */
                                         }
+                                        /* can be misaligned, thus memcpy */
+                                        memcpy(&server_addr, temp, 4);
+                                        xid = packet.xid;
+                                        requested_ip = packet.yiaddr;
+
+                                        /* enter requesting state */
+                                        state = REQUESTING;
+                                        timeout = 0;
+                                        packet_num = 0;
                                 }
-                                break;
+                                continue;
                         case RENEW_REQUESTED:
                         case REQUESTING:
                         case RENEWING:
@@ -503,13 +514,12 @@ int udhcpc_main(int argc, char **argv)
                                         temp = get_option(&packet, DHCP_LEASE_TIME);
                                         if (!temp) {
                                                 bb_error_msg("no lease time with ACK, using 1 hour lease");
-                                                lease = 60 * 60;
+                                                lease_seconds = 60 * 60;
                                         } else {
                                                 /* can be misaligned, thus memcpy */
-                                                memcpy(&lease, temp, 4);
-                                                lease = ntohl(lease);
+                                                memcpy(&lease_seconds, temp, 4);
+                                                lease_seconds = ntohl(lease_seconds);
                                         }
-
 #if ENABLE_FEATURE_UDHCPC_ARPING
                                         if (opt & OPT_a) {
                                                 if (!arpping(packet.yiaddr,
@@ -517,37 +527,37 @@ int udhcpc_main(int argc, char **argv)
                                                             client_config.arp,
                                                             client_config.interface)
                                                 ) {
-                                                        bb_info_msg("offered address is in use,"
-                                                                " declining");
+                                                        bb_info_msg("offered address is in use "
+                                                                "(got ARP reply), declining");
                                                         send_decline(xid, server_addr);
 
                                                         if (state != REQUESTING)
                                                                 udhcp_run_script(NULL, "deconfig");
+                                                        change_listen_mode(LISTEN_RAW);
                                                         state = INIT_SELECTING;
                                                         requested_ip = 0;
+                                                        timeout = decline_wait;
                                                         packet_num = 0;
-                                                        change_mode(LISTEN_RAW);
-                                                        timeout = now + decline_wait;
-                                                        break;
+                                                        continue; /* back to main loop */
                                                 }
                                         }
 #endif
                                         /* enter bound state */
-                                        t1 = lease / 2;
+                                        t1 = lease_seconds / 2;
 
                                         /* little fixed point for n * .875 */
-                                        t2 = (lease * 7) >> 3;
+                                        t2 = (lease_seconds * 7) >> 3;
                                         temp_addr.s_addr = packet.yiaddr;
                                         bb_info_msg("Lease of %s obtained, lease time %u",
-                                                inet_ntoa(temp_addr), (unsigned)lease);
-                                        start = now;
-                                        timeout = start + t1;
+                                                inet_ntoa(temp_addr), (unsigned)lease_seconds);
+                                        timestamp_got_lease = monotonic_sec();
+                                        timeout = t1;
                                         requested_ip = packet.yiaddr;
                                         udhcp_run_script(&packet,
                                                    ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 
                                         state = BOUND;
-                                        change_mode(LISTEN_NONE);
+                                        change_listen_mode(LISTEN_NONE);
                                         if (client_config.quit_after_lease) {
                                                 if (client_config.release_on_quit)
                                                         perform_release();
@@ -556,23 +566,30 @@ int udhcpc_main(int argc, char **argv)
                                         if (!client_config.foreground)
                                                 client_background();
 
-                                } else if (*message == DHCPNAK) {
+                                        continue; /* back to main loop */
+                                }
+                                if (*message == DHCPNAK) {
                                         /* return to init state */
                                         bb_info_msg("Received DHCP NAK");
                                         udhcp_run_script(&packet, "nak");
                                         if (state != REQUESTING)
                                                 udhcp_run_script(NULL, "deconfig");
+                                        change_listen_mode(LISTEN_RAW);
+                                        sleep(3); /* avoid excessive network traffic */
                                         state = INIT_SELECTING;
-                                        timeout = now;
                                         requested_ip = 0;
+                                        timeout = 0;
                                         packet_num = 0;
-                                        change_mode(LISTEN_RAW);
-                                        sleep(3); /* avoid excessive network traffic */
                                 }
-                                break;
+                                continue;
                         /* case BOUND, RELEASED: - ignore all packets */
                         }
-                } else {
+                        continue; /* back to main loop */
+                }
+
+                /* select() didn't timeout, something did happen.
+                 * But it wasn't a packet. It's a signal pipe then. */
+                {
                         int signo = udhcp_sp_read(&rfds);
                         switch (signo) {
                         case SIGUSR1:
@@ -588,7 +605,8 @@ int udhcpc_main(int argc, char **argv)
                                 goto ret0;
                         }
                 }
-        } /* for (;;) */
+        } /* for (;;) - main loop ends */
+
  ret0:
         retval = 0;
  ret: