4 files changed, 23 insertions, 4 deletions
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 3cbd2d3c8..cc0abd269 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -343,7 +343,8 @@ 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,
+		const char *ifname) 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/dhcpc.c b/networking/udhcp/dhcpc.c
index 66aa38c20..98720b45b 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -702,7 +702,8 @@ static int bcast_or_ucast(struct dhcp_packet *packet, uint32_t ciaddr, uint32_t
 	if (server)
 		return udhcp_send_kernel_packet(packet,
 			ciaddr, CLIENT_PORT,
-			server, SERVER_PORT);
+			server, SERVER_PORT,
+			client_data.interface);
 	return raw_bcast_from_client_data_ifindex(packet, ciaddr);
 }
 
diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index de16cf955..9e950ca1f 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -612,7 +612,8 @@ static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
 
 	udhcp_send_kernel_packet(dhcp_pkt,
 			server_data.server_nip, SERVER_PORT,
-			dhcp_pkt->gateway_nip, SERVER_PORT);
+			dhcp_pkt->gateway_nip, SERVER_PORT,
+			server_data.interface);
 }
 
 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 51374646d..4d8e005d4 100644
--- a/networking/udhcp/packet.c
+++ b/networking/udhcp/packet.c
@@ -189,7 +189,8 @@ 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,
+		const char *ifname)
 {
 	struct sockaddr_in sa;
 	unsigned padding;
@@ -204,6 +205,21 @@ int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
 	}
 	setsockopt_reuseaddr(fd);
 
+	/* If interface carrier goes down, unless we
+	 * bind socket to a particular netdev, the packet
+	 * can go out through another interface, eg. via
+	 * default route despite being bound to a specific
+	 * source IP. As such, bind to device hard and fail
+	 * otherwise. Sending renewal packets on foreign
+	 * interfaces makes no sense.
+	 */
+	if (ifname) {
+		if (setsockopt_bindtodevice(fd, ifname) < 0) {
+			msg = "bindtodevice";
+			goto ret_close;
+		}
+	}
+
 	memset(&sa, 0, sizeof(sa));
 	sa.sin_family = AF_INET;
 	sa.sin_port = htons(source_port);