5 files changed, 37 insertions, 16 deletions

diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index a9c23a186..04939e707 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -308,7 +308,9 @@ int udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
 
 int udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
                 uint32_t source_nip, int source_port,
-                uint32_t dest_nip, int dest_port) FAST_FUNC;
+                uint32_t dest_nip, int dest_port,
+                int send_flags
+) FAST_FUNC;
 
 void udhcp_sp_setup(void) FAST_FUNC;
 void udhcp_sp_fd_set(struct pollfd *pfds, int extra_fd) FAST_FUNC;
diff --git a/networking/udhcp/d6_dhcpc.c b/networking/udhcp/d6_dhcpc.c
index d4bb3507b..c13f23505 100644
--- a/networking/udhcp/d6_dhcpc.c
+++ b/networking/udhcp/d6_dhcpc.c
@@ -702,13 +702,15 @@ static NOINLINE int send_d6_renew(uint32_t xid, struct in6_addr *server_ipv6, st
         opt_ptr = add_d6_client_options(opt_ptr);
 
         bb_error_msg("sending %s", "renew");
-        if (server_ipv6)
+        if (server_ipv6) {
                 return d6_send_kernel_packet(
                         &packet, (opt_ptr - (uint8_t*) &packet),
                         our_cur_ipv6, CLIENT_PORT6,
                         server_ipv6, SERVER_PORT6,
                         client_config.ifindex
+                        /* TODO? send_flags: MSG_DONTROUTE (see IPv4 code for reason why) */
                 );
+        }
         return d6_mcast_from_client_config_ifindex(&packet, opt_ptr);
 }
 
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 6c74996ef..2ae8bcc4d 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -694,10 +694,16 @@ static int raw_bcast_from_client_config_ifindex(struct dhcp_packet *packet, uint
 
 static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t server)
 {
-        if (server)
+        if (server) {
+                /* Without MSG_DONTROUTE, the packet was seen routed over
+                 * _other interface_ if server ID is bogus (example: 1.1.1.1).
+                 */
                 return udhcp_send_kernel_packet(packet,
                         ciaddr, CLIENT_PORT,
-                        server, SERVER_PORT);
+                        server, SERVER_PORT,
+                        /*send_flags: "to hosts only on directly connected networks" */ MSG_DONTROUTE
+                );
+        }
         return raw_bcast_from_client_config_ifindex(packet, ciaddr);
 }
 
@@ -735,7 +741,7 @@ static NOINLINE int send_discover(uint32_t xid, uint32_t requested)
 static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requested)
 {
         struct dhcp_packet packet;
-        struct in_addr addr;
+        struct in_addr temp_addr;
 
 /*
  * RFC 2131 4.3.2 DHCPREQUEST message
@@ -766,8 +772,8 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
          */
         add_client_options(&packet);
 
-        addr.s_addr = requested;
-        bb_error_msg("sending select for %s", inet_ntoa(addr));
+        temp_addr.s_addr = requested;
+        bb_error_msg("sending select for %s", inet_ntoa(temp_addr));
         return raw_bcast_from_client_config_ifindex(&packet, INADDR_ANY);
 }
 
@@ -776,6 +782,7 @@ static NOINLINE int send_select(uint32_t xid, uint32_t server, uint32_t requeste
 static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
 {
         struct dhcp_packet packet;
+        struct in_addr temp_addr;
 
 /*
  * RFC 2131 4.3.2 DHCPREQUEST message
@@ -806,7 +813,8 @@ static NOINLINE int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
          */
         add_client_options(&packet);
 
-        bb_error_msg("sending %s", "renew");
+        temp_addr.s_addr = server;
+        bb_error_msg("sending renew to %s", inet_ntoa(temp_addr));
         return bcast_or_ucast(&packet, ciaddr, server);
 }
 
@@ -1524,11 +1532,17 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                          * Anyway, it does recover by eventually failing through
                          * into INIT_SELECTING state.
                          */
-                                        send_renew(xid, server_addr, requested_ip);
-                                        timeout >>= 1;
-                                        continue;
+                                        if (send_renew(xid, server_addr, requested_ip) >= 0) {
+                                                timeout >>= 1;
+                                                continue;
+                                        }
+                                        /* else: error sending.
+                                         * example: ENETUNREACH seen with server
+                                         * which gave us bogus server ID 1.1.1.1
+                                         * which wasn't reachable (and probably did not exist).
+                                         */
                                 }
-                                /* Timed out, enter rebinding state */
+                                /* Timed out or error, enter rebinding state */
                                 log1("entering rebinding state");
                                 state = REBINDING;
                                 /* fall right through */
diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index 05ddc8649..57d8b36c5 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -588,7 +588,9 @@ static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
 
         udhcp_send_kernel_packet(dhcp_pkt,
                         server_config.server_nip, SERVER_PORT,
-                        dhcp_pkt->gateway_nip, SERVER_PORT);
+                        dhcp_pkt->gateway_nip, SERVER_PORT,
+                        /*send_flags:*/ 0
+        );
 }
 
 static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c
index 44d9ceec7..ad0028bd0 100644
--- a/networking/udhcp/packet.c
+++ b/networking/udhcp/packet.c
@@ -191,7 +191,8 @@ int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
 /* Let the kernel do all the work for packet generation */
 int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
                 uint32_t source_nip, int source_port,
-                uint32_t dest_nip, int dest_port)
+                uint32_t dest_nip, int dest_port,
+                int send_flags)
 {
         struct sockaddr_in sa;
         unsigned padding;
@@ -228,8 +229,8 @@ int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
         padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
         if (padding > DHCP_SIZE - 300)
                 padding = DHCP_SIZE - 300;
-        result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
-        msg = "write";
+        result = send(fd, dhcp_pkt, DHCP_SIZE - padding, send_flags);
+        msg = "send";
  ret_close:
         close(fd);
         if (result < 0) {