sd-dhcp-client: use RFC4361-complient ClientID by default

In addition to the benefits listed in the RFC, this allows DHCP to work also in
case several interfaces share the same MAC address on the same link (IPVLAN).

Note that this will make the ClientID (so probably the assigned IP address)
change on upgrades. If it is desired to avoid that we would have to remember and
write back the ID (which the library supports, but networkd currently does not).

1 files changed, 51 insertions, 40 deletions

diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index 65e888adf2..5f90617b9e 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -36,9 +36,10 @@
 #include "dhcp-protocol.h"
 #include "dhcp-internal.h"
 #include "dhcp-lease-internal.h"
+#include "dhcp-identifier.h"
 #include "sd-dhcp-client.h"
 
-#define MAX_CLIENT_ID_LEN 64  /* Arbitrary limit */
+#define MAX_CLIENT_ID_LEN (sizeof(uint32_t) + MAX_DUID_LEN)  /* Arbitrary limit */
 #define MAX_MAC_ADDR_LEN INFINIBAND_ALEN
 
 struct sd_dhcp_client {
@@ -60,29 +61,31 @@ struct sd_dhcp_client {
         uint8_t mac_addr[MAX_MAC_ADDR_LEN];
         size_t mac_addr_len;
         uint16_t arp_type;
-        union {
-                struct {
-                        uint8_t type; /* 0: Generic (non-LL) (RFC 2132) */
-                        uint8_t data[MAX_CLIENT_ID_LEN];
-                } _packed_ gen;
-                struct {
-                        uint8_t type; /* 1: Ethernet Link-Layer (RFC 2132) */
-                        uint8_t haddr[ETH_ALEN];
-                } _packed_ eth;
-                struct {
-                        uint8_t type; /* 2 - 254: ARP/Link-Layer (RFC 2132) */
-                        uint8_t haddr[0];
-                } _packed_ ll;
-                struct {
-                        uint8_t type; /* 255: Node-specific (RFC 4361) */
-                        uint8_t iaid[4];
-                        uint8_t duid[MAX_CLIENT_ID_LEN - 4];
-                } _packed_ ns;
-                struct {
-                        uint8_t type;
-                        uint8_t data[MAX_CLIENT_ID_LEN];
-                } _packed_ raw;
-        } client_id;
+        struct {
+                uint8_t type;
+                union {
+                        struct {
+                                /* 0: Generic (non-LL) (RFC 2132) */
+                                uint8_t data[MAX_CLIENT_ID_LEN];
+                        } _packed_ gen;
+                        struct {
+                                /* 1: Ethernet Link-Layer (RFC 2132) */
+                                uint8_t haddr[ETH_ALEN];
+                        } _packed_ eth;
+                        struct {
+                                /* 2 - 254: ARP/Link-Layer (RFC 2132) */
+                                uint8_t haddr[0];
+                        } _packed_ ll;
+                        struct {
+                                /* 255: Node-specific (RFC 4361) */
+                                uint32_t iaid;
+                                struct duid duid;
+                        } _packed_ ns;
+                        struct {
+                                uint8_t data[MAX_CLIENT_ID_LEN];
+                        } _packed_ raw;
+                };
+        } _packed_ client_id;
         size_t client_id_len;
         char *hostname;
         char *vendor_class_identifier;
@@ -239,10 +242,9 @@ int sd_dhcp_client_get_client_id(sd_dhcp_client *client, uint8_t *type,
         *data = NULL;
         *data_len = 0;
         if (client->client_id_len) {
-                *type = client->client_id.raw.type;
+                *type = client->client_id.type;
                 *data = client->client_id.raw.data;
-                *data_len = client->client_id_len -
-                        sizeof (client->client_id.raw.type);
+                *data_len = client->client_id_len - sizeof(client->client_id.type);
         }
 
         return 0;
@@ -270,8 +272,8 @@ int sd_dhcp_client_set_client_id(sd_dhcp_client *client, uint8_t type,
                 break;
         }
 
-        if (client->client_id_len == data_len + sizeof (client->client_id.raw.type) &&
-            client->client_id.raw.type == type &&
+        if (client->client_id_len == data_len + sizeof(client->client_id.type) &&
+            client->client_id.type == type &&
             memcmp(&client->client_id.raw.data, data, data_len) == 0)
                 return 0;
 
@@ -282,9 +284,9 @@ int sd_dhcp_client_set_client_id(sd_dhcp_client *client, uint8_t type,
                 client_stop(client, DHCP_EVENT_STOP);
         }
 
-        client->client_id.raw.type = type;
+        client->client_id.type = type;
         memcpy(&client->client_id.raw.data, data, data_len);
-        client->client_id_len = data_len + sizeof (client->client_id.raw.type);
+        client->client_id_len = data_len + sizeof (client->client_id.type);
 
         if (need_restart && client->state != DHCP_STATE_STOPPED)
                 sd_dhcp_client_start(client);
@@ -461,12 +463,21 @@ static int client_message_init(sd_dhcp_client *client, DHCPPacket **ret,
         if (client->arp_type == ARPHRD_ETHER)
                 memcpy(&packet->dhcp.chaddr, &client->mac_addr, ETH_ALEN);
 
-        /* If no client identifier exists, construct one from an ethernet
-           address if present */
-        if (client->client_id_len == 0 && client->arp_type == ARPHRD_ETHER) {
-                client->client_id.eth.type = ARPHRD_ETHER;
-                memcpy(&client->client_id.eth.haddr, &client->mac_addr, ETH_ALEN);
-                client->client_id_len = sizeof (client->client_id.eth);
+        /* If no client identifier exists, construct an RFC 4361-compliant one */
+        if (client->client_id_len == 0) {
+                size_t duid_len;
+
+                client->client_id.type = 255;
+
+                r = dhcp_identifier_set_iaid(client->index, client->mac_addr, client->mac_addr_len, &client->client_id.ns.iaid);
+                if (r < 0)
+                        return r;
+
+                r = dhcp_identifier_set_duid_en(&client->client_id.ns.duid, &duid_len);
+                if (r < 0)
+                        return r;
+
+                client->client_id_len = sizeof(client->client_id.type) + sizeof(client->client_id.ns.iaid) + duid_len;
         }
 
         /* Some DHCP servers will refuse to issue an DHCP lease if the Client
@@ -475,7 +486,7 @@ static int client_message_init(sd_dhcp_client *client, DHCPPacket **ret,
                 r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, 0,
                                        DHCP_OPTION_CLIENT_IDENTIFIER,
                                        client->client_id_len,
-                                       &client->client_id.raw);
+                                       &client->client_id);
                 if (r < 0)
                         return r;
         }
@@ -1031,7 +1042,7 @@ static int client_handle_offer(sd_dhcp_client *client, DHCPMessage *offer,
 
         if (client->client_id_len) {
                 r = dhcp_lease_set_client_id(lease,
-                                             (uint8_t *) &client->client_id.raw,
+                                             (uint8_t *) &client->client_id,
                                              client->client_id_len);
                 if (r < 0)
                         return r;
@@ -1098,7 +1109,7 @@ static int client_handle_ack(sd_dhcp_client *client, DHCPMessage *ack,
 
         if (client->client_id_len) {
                 r = dhcp_lease_set_client_id(lease,
-                                             (uint8_t *) &client->client_id.raw,
+                                             (uint8_t *) &client->client_id,
                                              client->client_id_len);
                 if (r < 0)
                         return r;