udhcpc: an option to perform ARP check (Jonas Danielsson <jonas.danielsson@axis.com>)

configurable, ~+300 bytes when on.

1 files changed, 53 insertions, 12 deletions

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index c6f9fe42d..b3b89459e 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -145,6 +145,13 @@ int udhcpc_main(int argc, char **argv)
 {
         uint8_t *temp, *message;
         char *str_c, *str_V, *str_h, *str_F, *str_r, *str_T, *str_A, *str_t;
+        int tryagain_timeout = 60;
+        int discover_timeout = 3;
+        int discover_retries = 3;
+#if ENABLE_FEATURE_UDHCPC_ARPING
+        int decline_wait = 10;
+        char *str_W;
+#endif
         uint32_t xid = 0;
         uint32_t lease = 0; /* can be given as 32-bit quantity */
         unsigned t1 = 0, t2 = 0; /* what a wonderful names */
@@ -180,6 +187,10 @@ int udhcpc_main(int argc, char **argv)
                 OPT_v = 1 << 17,
                 OPT_S = 1 << 18,
                 OPT_A = 1 << 19,
+#if ENABLE_FEATURE_UDHCPC_ARPING
+                OPT_a = 1 << 20,
+                OPT_W = 1 << 21,
+#endif
         };
 #if ENABLE_GETOPT_LONG
         static const char udhcpc_longopts[] ALIGN1 =
@@ -203,14 +214,15 @@ int udhcpc_main(int argc, char **argv)
                 "retries\0"       Required_argument "t"
                 "tryagain\0"      Required_argument "A"
                 "syslog\0"        No_argument       "S"
+#if ENABLE_FEATURE_UDHCPC_ARPING
+                "arping\0"        No_argument       "a"
+                "wait\0"          Required_argument "W"
+#endif
                 ;
 #endif
         /* Default options. */
         client_config.interface = "eth0";
         client_config.script = DEFAULT_SCRIPT;
-        client_config.retries = 3;
-        client_config.timeout = 3;
-        client_config.tryagain = 60;
 
         /* Parse command line */
         opt_complementary = "c--C:C--c" // mutually exclusive
@@ -218,10 +230,12 @@ int udhcpc_main(int argc, char **argv)
 #if ENABLE_GETOPT_LONG
         applet_long_options = udhcpc_longopts;
 #endif
-        opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:",
-                &str_c, &str_V, &str_h, &str_h, &str_F,
+        opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:"
+                USE_FEATURE_UDHCPC_ARPING("aW:")
+                , &str_c, &str_V, &str_h, &str_h, &str_F,
                 &client_config.interface, &client_config.pidfile, &str_r,
                 &client_config.script, &str_T, &str_t, &str_A
+                USE_FEATURE_UDHCPC_ARPING(, &str_W)
                 );
 
         if (opt & OPT_c)
@@ -259,11 +273,11 @@ int udhcpc_main(int argc, char **argv)
                 requested_ip = inet_addr(str_r);
         // if (opt & OPT_s) client_config.script = ...
         if (opt & OPT_T)
-                client_config.timeout = xatoi_u(str_T);
+                discover_timeout = xatoi_u(str_T);
         if (opt & OPT_t)
-                client_config.retries = xatoi_u(str_t);
+                discover_retries = xatoi_u(str_t);
         if (opt & OPT_A)
-                client_config.tryagain = xatoi_u(str_A);
+                tryagain_timeout = xatoi_u(str_A);
         if (opt & OPT_v) {
                 puts("version "BB_VER);
                 return 0;
@@ -274,6 +288,11 @@ int udhcpc_main(int argc, char **argv)
                 logmode |= LOGMODE_SYSLOG;
         }
 
+#if ENABLE_FEATURE_UDHCPC_ARPING
+        if (opt & OPT_W)
+                decline_wait = xatou_range(str_W, 10, INT_MAX);
+#endif
+
         if (read_interface(client_config.interface, &client_config.ifindex,
                            NULL, client_config.arp))
                 return 1;
@@ -339,14 +358,14 @@ int udhcpc_main(int argc, char **argv)
                         /* timeout dropped to zero */
                         switch (state) {
                         case INIT_SELECTING:
-                                if (packet_num < client_config.retries) {
+                                if (packet_num < discover_retries) {
                                         if (packet_num == 0)
                                                 xid = random_xid();
 
                                         /* send discover packet */
                                         send_discover(xid, requested_ip); /* broadcast */
 
-                                        timeout = now + client_config.timeout;
+                                        timeout = now + discover_timeout;
                                         packet_num++;
                                 } else {
                                         udhcp_run_script(NULL, "leasefail");
@@ -360,12 +379,12 @@ int udhcpc_main(int argc, char **argv)
                                         }
                                         /* wait to try again */
                                         packet_num = 0;
-                                        timeout = now + client_config.tryagain;
+                                        timeout = now + tryagain_timeout;
                                 }
                                 break;
                         case RENEW_REQUESTED:
                         case REQUESTING:
-                                if (packet_num < client_config.retries) {
+                                if (packet_num < discover_retries) {
                                         /* send request packet */
                                         if (state == RENEW_REQUESTED)
                                                 send_renew(xid, server_addr, requested_ip); /* unicast */
@@ -491,6 +510,28 @@ int udhcpc_main(int argc, char **argv)
                                                 lease = ntohl(lease);
                                         }
 
+#if ENABLE_FEATURE_UDHCPC_ARPING
+                                        if (opt & OPT_a) {
+                                                if (!arpping(packet.yiaddr,
+                                                            (uint32_t) 0,
+                                                            client_config.arp,
+                                                            client_config.interface)
+                                                ) {
+                                                        bb_info_msg("offered address is in use,"
+                                                                " declining");
+                                                        send_decline(xid, server_addr);
+
+                                                        if (state != REQUESTING)
+                                                                udhcp_run_script(NULL, "deconfig");
+                                                        state = INIT_SELECTING;
+                                                        requested_ip = 0;
+                                                        packet_num = 0;
+                                                        change_mode(LISTEN_RAW);
+                                                        timeout = now + decline_wait;
+                                                        break;
+                                                }
+                                        }
+#endif
                                         /* enter bound state */
                                         t1 = lease / 2;