9 files changed, 138 insertions, 47 deletions

diff --git a/include/usage.h b/include/usage.h
index d0eecdb4a..3c8762ee1 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -2183,8 +2183,8 @@
        "and * (run both after creating and before deleting). The commands run in\n" \
        "the /dev directory, and use system() which calls /bin/sh.\n\n" \
         ) \
-       "Config file parsing stops on the first matching line. If no config\n"\
-       "entry is matched, devices are created with default 0:0 660. (Make\n"\
+       "Config file parsing stops on the first matching line. If no config\n" \
+       "entry is matched, devices are created with default 0:0 660. (Make\n" \
        "the last line match .* to override this.)\n\n" \
         )
 
@@ -3843,44 +3843,50 @@ USE_FEATURE_RUN_PARTS_FANCY("\n	-l	Prints names of all matching files even when
        "        [-p pidfile] [-r IP] [-s script]"
 #define udhcpc_full_usage \
         USE_GETOPT_LONG( \
-       "        -V,--vendorclass=CLASSID        Set vendor class identifier" \
-       "\n      -i,--interface=INTERFACE        Interface to use (default: eth0)" \
+       "        -V,--vendorclass=CLASSID        Vendor class identifier" \
+       "\n      -i,--interface=INTERFACE        Interface to use (default eth0)" \
        "\n      -H,-h,--hostname=HOSTNAME       Client hostname" \
-       "\n      -c,--clientid=CLIENTID  Set client identifier" \
+       "\n      -c,--clientid=CLIENTID  Client identifier" \
        "\n      -C,--clientid-none      Suppress default client identifier" \
-       "\n      -p,--pidfile=file       Store process ID of daemon in file" \
+       "\n      -p,--pidfile=file       Create pidfile" \
        "\n      -r,--request=IP         IP address to request" \
        "\n      -s,--script=file        Run file at dhcp events (default: /usr/share/udhcpc/default.script)" \
-       "\n      -t,--retries=N          Send up to N request packets"\
-       "\n      -T,--timeout=N          Try to get a lease for N seconds (default: 3)"\
-       "\n      -A,--tryagain=N         Wait N seconds (default: 60) after failure"\
+       "\n      -t,--retries=N          Send up to N request packets" \
+       "\n      -T,--timeout=N          Try to get a lease for N seconds (default 3)" \
+       "\n      -A,--tryagain=N         Wait N seconds (default 60) after failure" \
        "\n      -f,--foreground Run in foreground" \
-       "\n      -b,--background Background if lease cannot be immediately negotiated" \
+       "\n      -b,--background Background if lease is not immediately obtained" \
        "\n      -S,--syslog     Log to syslog too" \
-       "\n      -n,--now        Exit with failure if lease cannot be immediately negotiated" \
+       "\n      -n,--now        Exit with failure if lease is not immediately obtained" \
        "\n      -q,--quit       Quit after obtaining lease" \
        "\n      -R,--release    Release IP on quit" \
-       "\n      -v,--version    Display version" \
+        USE_FEATURE_UDHCPC_ARPING( \
+       "\n      -a,--arping     Use arping to validate offered address" \
+       "\n      -W,--wait=N     Wait N seconds after declining (default 10)" \
+        ) \
         ) \
         SKIP_GETOPT_LONG( \
-       "        -V CLASSID      Set vendor class identifier" \
+       "        -V CLASSID      Vendor class identifier" \
        "\n      -i INTERFACE    Interface to use (default: eth0)" \
        "\n      -H,-h HOSTNAME  Client hostname" \
-       "\n      -c CLIENTID     Set client identifier" \
+       "\n      -c CLIENTID     Client identifier" \
        "\n      -C              Suppress default client identifier" \
-       "\n      -p file         Store process ID of daemon in file" \
+       "\n      -p file         Create pidfile" \
        "\n      -r IP           IP address to request" \
        "\n      -s file         Run file at dhcp events (default: /usr/share/udhcpc/default.script)" \
-       "\n      -t N            Send up to N request packets"\
-       "\n      -T N            Try to get a lease for N seconds (default: 3)"\
-       "\n      -A N            Wait N seconds (default: 60) after failure"\
+       "\n      -t N            Send up to N request packets" \
+       "\n      -T N            Try to get a lease for N seconds (default 3)" \
+       "\n      -A N            Wait N seconds (default 60) after failure" \
        "\n      -f              Run in foreground" \
-       "\n      -b              Background if lease cannot be immediately negotiated" \
+       "\n      -b              Background if lease is not immediately obtained" \
        "\n      -S              Log to syslog too" \
-       "\n      -n              Exit with failure if lease cannot be immediately negotiated" \
+       "\n      -n              Exit with failure if lease is not immediately obtained" \
        "\n      -q              Quit after obtaining lease" \
        "\n      -R              Release IP on quit" \
-       "\n      -v              Display version" \
+        USE_FEATURE_UDHCPC_ARPING( \
+       "\n      -a              Use arping to validate offered address" \
+       "\n      -W N            Wait N seconds after declining (default 10)" \
+        ) \
         )
 
 #define udhcpd_trivial_usage \
diff --git a/networking/udhcp/Config.in b/networking/udhcp/Config.in
index 76b078001..734db65cc 100644
--- a/networking/udhcp/Config.in
+++ b/networking/udhcp/Config.in
@@ -54,6 +54,16 @@ config APP_UDHCPC
 
           See http://udhcp.busybox.net for further details.
 
+config FEATURE_UDHCPC_ARPING
+        bool "Ask udhcpc to verify that the offered address is free, using arpping"
+        default y
+        depends on APP_UDHCPC
+        help
+          If selected, udhcpc will use arpping to make sure the offered address
+          is really available. The client will DHCPDECLINE the offer if the
+          address is in use, and restart the discover process.
+
+
 config FEATURE_UDHCP_DEBUG
         bool "Compile udhcp with noisy debugging messages"
         default n
diff --git a/networking/udhcp/Kbuild b/networking/udhcp/Kbuild
index aed40b98c..7d4747083 100644
--- a/networking/udhcp/Kbuild
+++ b/networking/udhcp/Kbuild
@@ -10,10 +10,16 @@ lib-$(CONFIG_APP_UDHCPC)        += common.o options.o packet.o \
                                    signalpipe.o socket.o
 lib-$(CONFIG_APP_UDHCPD)        += common.o options.o packet.o \
                                    signalpipe.o socket.o
+
 lib-$(CONFIG_APP_UDHCPC)        += dhcpc.o clientpacket.o clientsocket.o \
                                    script.o
+
+UDHCPC_NEEDS_ARPING-$(CONFIG_FEATURE_UDHCPC_ARPING) = y
+lib-$(UDHCPC_NEEDS_ARPING)      += arpping.o
+
 lib-$(CONFIG_APP_UDHCPD)        += dhcpd.o arpping.o files.o leases.o \
                                    serverpacket.o static_leases.o
+
 lib-$(CONFIG_APP_DUMPLEASES)    += dumpleases.o
 lib-$(CONFIG_APP_DHCPRELAY)     += dhcprelay.o
 lib-$(CONFIG_FEATURE_RFC3397)   += domain_codec.o
diff --git a/networking/udhcp/arpping.c b/networking/udhcp/arpping.c
index 7b702d8f3..45597c04b 100644
--- a/networking/udhcp/arpping.c
+++ b/networking/udhcp/arpping.c
@@ -32,12 +32,16 @@ struct arpMsg {
         uint8_t  pad[18];       /* 2a pad for min. ethernet payload (60 bytes) */
 } ATTRIBUTE_PACKED;
 
+enum {
+        ARP_MSG_SIZE = 0x2a
+};
+
 
 /* Returns 1 if no reply received */
 
 int arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *interface)
 {
-        int timeout_ms = 2000;
+        int timeout_ms;
         struct pollfd pfd[1];
 #define s (pfd[0].fd)           /* socket */
         int rv = 1;             /* "no reply received" yet */
@@ -51,7 +55,7 @@ int arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *i
         }
 
         if (setsockopt_broadcast(s) == -1) {
-                bb_perror_msg("cannot setsocketopt on raw socket");
+                bb_perror_msg("cannot enable bcast on raw socket");
                 goto ret;
         }
 
@@ -67,28 +71,35 @@ int arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *i
         arp.operation = htons(ARPOP_REQUEST);           /* ARP op code */
         memcpy(arp.sHaddr, from_mac, 6);                /* source hardware address */
         memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */
-        /* tHaddr */                                    /* target hardware address */
+        /* tHaddr is zero-fiiled */                     /* target hardware address */
         memcpy(arp.tInaddr, &test_ip, sizeof(test_ip)); /* target IP address */
 
         memset(&addr, 0, sizeof(addr));
         safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data));
-        if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0)
+        if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) {
+                // TODO: error message? caller didn't expect us to fail,
+                // just returning 1 "no reply received" misleads it.
                 goto ret;
+        }
 
         /* wait for arp reply, and check it */
+        timeout_ms = 2000;
         do {
                 int r;
                 unsigned prevTime = monotonic_us();
 
                 pfd[0].events = POLLIN;
                 r = safe_poll(pfd, 1, timeout_ms);
-                if (r < 0) {
+                if (r < 0)
                         break;
-                } else if (r) {
-                        if (read(s, &arp, sizeof(arp)) < 0)
+                if (r) {
+                        r = read(s, &arp, sizeof(arp));
+                        if (r < 0)
                                 break;
-                        if (arp.operation == htons(ARPOP_REPLY)
-                         && memcmp(arp.tHaddr, from_mac, 6) == 0
+                        if (r >= ARP_MSG_SIZE
+                         && arp.operation == htons(ARPOP_REPLY)
+                         /* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */
+                         /* && memcmp(arp.tHaddr, from_mac, 6) == 0 */
                          && *((uint32_t *) arp.sInaddr) == test_ip
                         ) {
                                 rv = 0;
diff --git a/networking/udhcp/clientpacket.c b/networking/udhcp/clientpacket.c
index 42b4895e5..e7eeb58b1 100644
--- a/networking/udhcp/clientpacket.c
+++ b/networking/udhcp/clientpacket.c
@@ -69,6 +69,22 @@ static void add_requests(struct dhcpMessage *packet)
 
 }
 
+#if ENABLE_FEATURE_UDHCPC_ARPING
+/* Unicast a DHCP decline message */
+int send_decline(uint32_t xid, uint32_t server)
+{
+        struct dhcpMessage packet;
+
+        init_packet(&packet, DHCPDECLINE);
+        packet.xid = xid;
+        add_requests(&packet);
+
+        bb_info_msg("Sending decline...");
+
+        return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
+                SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
+}
+#endif
 
 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 int send_discover(uint32_t xid, uint32_t requested)
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 4864c8565..179c21fdb 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -76,7 +76,7 @@ void udhcp_run_script(struct dhcpMessage *packet, const char *name);
 
 void udhcp_sp_setup(void);
 int udhcp_sp_fd_set(fd_set *rfds, int extra_fd);
-int udhcp_sp_read(fd_set *rfds);
+int udhcp_sp_read(const fd_set *rfds);
 int raw_socket(int ifindex);
 int read_interface(const char *interface, int *ifindex, uint32_t *addr, uint8_t *arp);
 int listen_socket(/*uint32_t ip,*/ int port, const char *inf);
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;
 
diff --git a/networking/udhcp/dhcpc.h b/networking/udhcp/dhcpc.h
index 72a8bd94f..c0172a84f 100644
--- a/networking/udhcp/dhcpc.h
+++ b/networking/udhcp/dhcpc.h
@@ -1,5 +1,6 @@
 /* vi: set sw=4 ts=4: */
 /* dhcpc.h */
+
 #ifndef _DHCPC_H
 #define _DHCPC_H
 
@@ -28,9 +29,6 @@ struct client_config_t {
         uint8_t *hostname;              /* Optional hostname to use */
         uint8_t *fqdn;                  /* Optional fully qualified domain name to use */
         int ifindex;                    /* Index number of the interface to use */
-        int retries;                    /* Max number of request packets */
-        int timeout;                    /* Number of seconds to try to get a lease */
-        int tryagain;                   /* Number of seconds to try to get a lease */
         uint8_t arp[6];                 /* Our arp address */
 };
 
@@ -42,6 +40,9 @@ struct client_config_t {
 uint32_t random_xid(void);
 int send_discover(uint32_t xid, uint32_t requested);
 int send_selecting(uint32_t xid, uint32_t server, uint32_t requested);
+#if ENABLE_FEATURE_UDHCPC_ARPING
+int send_decline(uint32_t xid, uint32_t server);
+#endif
 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr);
 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr);
 int send_release(uint32_t server, uint32_t ciaddr);
diff --git a/networking/udhcp/signalpipe.c b/networking/udhcp/signalpipe.c
index fafd2082a..845aa3a9a 100644
--- a/networking/udhcp/signalpipe.c
+++ b/networking/udhcp/signalpipe.c
@@ -66,7 +66,7 @@ int udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
 /* Read a signal from the signal pipe. Returns 0 if there is
  * no signal, -1 on error (and sets errno appropriately), and
  * your signal on success */
-int udhcp_sp_read(fd_set *rfds)
+int udhcp_sp_read(const fd_set *rfds)
 {
         unsigned char sig;