dhcp: bind udp sockets to interfaces (#4822)

5 files changed, 18 insertions, 6 deletions

diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
index 5aa8aca426..3fdf02da3e 100644
--- a/src/libsystemd-network/dhcp-internal.h
+++ b/src/libsystemd-network/dhcp-internal.h
@@ -30,11 +30,11 @@
 #include "dhcp-protocol.h"
 #include "socket-util.h"
 
-int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
+int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
                                  uint32_t xid, const uint8_t *mac_addr,
                                  size_t mac_addr_len, uint16_t arp_type,
                                  uint16_t port);
-int dhcp_network_bind_udp_socket(be32_t address, uint16_t port);
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port);
 int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
                                  const void *packet, size_t len);
 int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
index 3c85bb0b54..65405dcce0 100644
--- a/src/libsystemd-network/dhcp-network.c
+++ b/src/libsystemd-network/dhcp-network.c
@@ -19,6 +19,7 @@
 
 #include <errno.h>
 #include <net/ethernet.h>
+#include <net/if.h>
 #include <net/if_arp.h>
 #include <stdio.h>
 #include <string.h>
@@ -156,13 +157,14 @@ int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
                                 bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 }
 
-int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
         union sockaddr_union src = {
                 .in.sin_family = AF_INET,
                 .in.sin_port = htobe16(port),
                 .in.sin_addr.s_addr = address,
         };
         _cleanup_close_ int s = -1;
+        char ifname[IF_NAMESIZE] = "";
         int r, on = 1, tos = IPTOS_CLASS_CS6;
 
         s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
@@ -177,6 +179,15 @@ int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
         if (r < 0)
                 return -errno;
 
+        if (ifindex > 0) {
+                if (if_indextoname(ifindex, ifname) == 0)
+                        return -errno;
+
+                r = setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, ifname, strlen(ifname));
+                if (r < 0)
+                        return -errno;
+        }
+
         if (address == INADDR_ANY) {
                 r = setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
                 if (r < 0)
@@ -185,6 +196,7 @@ int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
                 r = setsockopt(s, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on));
                 if (r < 0)
                         return -errno;
+
         } else {
                 r = setsockopt(s, IPPROTO_IP, IP_FREEBIND, &on, sizeof(on));
                 if (r < 0)
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index 1423264806..b4bf75a3dc 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -1546,7 +1546,7 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, i
                                 goto error;
                         }
 
-                        r = dhcp_network_bind_udp_socket(client->lease->address, client->port);
+                        r = dhcp_network_bind_udp_socket(client->ifindex, client->lease->address, client->port);
                         if (r < 0) {
                                 log_dhcp_client(client, "could not bind UDP socket");
                                 goto error;
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index f16314a37f..0e57ab6b69 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -1022,7 +1022,7 @@ int sd_dhcp_server_start(sd_dhcp_server *server) {
         }
         server->fd_raw = r;
 
-        r = dhcp_network_bind_udp_socket(INADDR_ANY, DHCP_PORT_SERVER);
+        r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_ANY, DHCP_PORT_SERVER);
         if (r < 0) {
                 sd_dhcp_server_stop(server);
                 return r;
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
index c10ca74b86..f5f1284e6d 100644
--- a/src/libsystemd-network/test-dhcp-client.c
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -203,7 +203,7 @@ int dhcp_network_bind_raw_socket(
         return test_fd[0];
 }
 
-int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port) {
         int fd;
 
         fd = socket(AF_INET, SOCK_DGRAM|SOCK_CLOEXEC, 0);