networkd: support setting dhcp client listen port (#4631)

Allow setting custom port for the DHCP client to listen on in networkd.

[DHCP]
ListenPort=6677

5 files changed, 32 insertions, 16 deletions

diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
index 99f690897d..5aa8aca426 100644
--- a/src/libsystemd-network/dhcp-internal.h
+++ b/src/libsystemd-network/dhcp-internal.h
@@ -32,7 +32,8 @@
 
 int dhcp_network_bind_raw_socket(int index, union sockaddr_union *link,
                                  uint32_t xid, const uint8_t *mac_addr,
-                                 size_t mac_addr_len, uint16_t arp_type);
+                                 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_send_raw_socket(int s, const union sockaddr_union *link,
                                  const void *packet, size_t len);
@@ -57,7 +58,7 @@ void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
                                    uint16_t source, be32_t destination_addr,
                                    uint16_t destination, uint16_t len);
 
-int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum);
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port);
 
 /* If we are invoking callbacks of a dhcp-client, ensure unreffing the
  * client from the callback doesn't destroy the object we are working
diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
index a9f5a0a5de..3c85bb0b54 100644
--- a/src/libsystemd-network/dhcp-network.c
+++ b/src/libsystemd-network/dhcp-network.c
@@ -36,7 +36,8 @@ static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
                             size_t mac_addr_len,
                             const uint8_t *bcast_addr,
                             const struct ether_addr *eth_mac,
-                            uint16_t arp_type, uint8_t dhcp_hlen) {
+                            uint16_t arp_type, uint8_t dhcp_hlen,
+                            uint16_t port) {
         struct sock_filter filter[] = {
                 BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
                 BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
@@ -53,7 +54,7 @@ static int _bind_raw_socket(int ifindex, union sockaddr_union *link,
                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
                 BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
-                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_PORT_CLIENT, 1, 0),           /* UDP destination port == DHCP client port ? */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
                 BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
                 BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
                 BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
@@ -125,7 +126,8 @@ static int _bind_raw_socket(int ifindex, 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) {
+                                 size_t mac_addr_len, uint16_t arp_type,
+                                 uint16_t port) {
         static const uint8_t eth_bcast[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
         /* Default broadcast address for IPoIB */
         static const uint8_t ib_bcast[] = {
@@ -151,7 +153,7 @@ int dhcp_network_bind_raw_socket(int ifindex, union sockaddr_union *link,
                 return -EINVAL;
 
         return _bind_raw_socket(ifindex, link, xid, mac_addr, mac_addr_len,
-                                bcast_addr, &eth_mac, arp_type, dhcp_hlen);
+                                bcast_addr, &eth_mac, arp_type, dhcp_hlen, port);
 }
 
 int dhcp_network_bind_udp_socket(be32_t address, uint16_t port) {
diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
index 8be774061d..40442b3636 100644
--- a/src/libsystemd-network/dhcp-packet.c
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -114,7 +114,7 @@ void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
         packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE);
 }
 
-int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port) {
         size_t hdrlen;
 
         assert(packet);
@@ -160,10 +160,10 @@ int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
                 return -EINVAL;
         }
 
-        if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
+        if (be16toh(packet->udp.dest) != port) {
                 log_debug("ignoring packet: to port %u, which "
                           "is not the DHCP client port (%u)",
-                          be16toh(packet->udp.dest), DHCP_PORT_CLIENT);
+                          be16toh(packet->udp.dest), port);
                 return -EINVAL;
         }
 
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index 5ccb23922c..6475da2c2a 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -55,6 +55,7 @@ struct sd_dhcp_client {
         sd_event_source *timeout_resend;
         int ifindex;
         int fd;
+        uint16_t port;
         union sockaddr_union link;
         sd_event_source *receive_message;
         bool request_broadcast;
@@ -426,6 +427,17 @@ int sd_dhcp_client_set_vendor_class_identifier(
         return 0;
 }
 
+int sd_dhcp_client_set_client_port(
+                sd_dhcp_client *client,
+                uint16_t port) {
+
+        assert_return(client, -EINVAL);
+
+        client->port = port;
+
+        return 0;
+}
+
 int sd_dhcp_client_set_mtu(sd_dhcp_client *client, uint32_t mtu) {
         assert_return(client, -EINVAL);
         assert_return(mtu >= DHCP_DEFAULT_MIN_SIZE, -ERANGE);
@@ -668,7 +680,7 @@ static int dhcp_client_send_raw(
                 DHCPPacket *packet,
                 size_t len) {
 
-        dhcp_packet_append_ip_headers(packet, INADDR_ANY, DHCP_PORT_CLIENT,
+        dhcp_packet_append_ip_headers(packet, INADDR_ANY, client->port,
                                       INADDR_BROADCAST, DHCP_PORT_SERVER, len);
 
         return dhcp_network_send_raw_socket(client->fd, &client->link,
@@ -1120,7 +1132,7 @@ static int client_start_delayed(sd_dhcp_client *client) {
 
         r = dhcp_network_bind_raw_socket(client->ifindex, &client->link,
                                          client->xid, client->mac_addr,
-                                         client->mac_addr_len, client->arp_type);
+                                         client->mac_addr_len, client->arp_type, client->port);
         if (r < 0) {
                 client_stop(client, r);
                 return r;
@@ -1170,7 +1182,8 @@ static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata)
 
         r = dhcp_network_bind_raw_socket(client->ifindex, &client->link,
                                          client->xid, client->mac_addr,
-                                         client->mac_addr_len, client->arp_type);
+                                         client->mac_addr_len, client->arp_type,
+                                         client->port);
         if (r < 0) {
                 client_stop(client, r);
                 return 0;
@@ -1555,8 +1568,7 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, i
                                 goto error;
                         }
 
-                        r = dhcp_network_bind_udp_socket(client->lease->address,
-                                                         DHCP_PORT_CLIENT);
+                        r = dhcp_network_bind_udp_socket(client->lease->address, client->port);
                         if (r < 0) {
                                 log_dhcp_client(client, "could not bind UDP socket");
                                 goto error;
@@ -1766,7 +1778,7 @@ static int client_receive_message_raw(
                 }
         }
 
-        r = dhcp_packet_verify_headers(packet, len, checksum);
+        r = dhcp_packet_verify_headers(packet, len, checksum, client->port);
         if (r < 0)
                 return 0;
 
@@ -1891,6 +1903,7 @@ int sd_dhcp_client_new(sd_dhcp_client **ret) {
         client->fd = -1;
         client->attempt = 1;
         client->mtu = DHCP_DEFAULT_MIN_SIZE;
+        client->port = DHCP_PORT_CLIENT;
 
         client->req_opts_size = ELEMENTSOF(default_req_opts);
         client->req_opts = memdup(default_req_opts, client->req_opts_size);
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
index 2a101cb1fe..c10ca74b86 100644
--- a/src/libsystemd-network/test-dhcp-client.c
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -195,7 +195,7 @@ int dhcp_network_bind_raw_socket(
                 union sockaddr_union *link,
                 uint32_t id,
                 const uint8_t *addr, size_t addr_len,
-                uint16_t arp_type) {
+                uint16_t arp_type, uint16_t port) {
 
         if (socketpair(AF_UNIX, SOCK_STREAM, 0, test_fd) < 0)
                 return -errno;