sd-dhcp6-client: Receive and parse Advertise messages

When receiving DHCPv6 messages, discard the ones that are not meant
for DHCPv6 clients and verify the transaction id. Once that is done,
process the Advertise message and select the Advertise with the
highest preference.

Create a separate function for lease information parsing so that it
can be reused in other parts of the protocol. Verify both DUID and
IAID in the received message and store other necessary information
with the lease structure.

3 files changed, 224 insertions, 2 deletions

diff --git a/src/libsystemd-network/dhcp6-internal.h b/src/libsystemd-network/dhcp6-internal.h
index ec1d82abee..94e3a5d408 100644
--- a/src/libsystemd-network/dhcp6-internal.h
+++ b/src/libsystemd-network/dhcp6-internal.h
@@ -75,3 +75,5 @@ int dhcp6_network_send_udp_socket(int s, struct in6_addr *address,
 
 const char *dhcp6_message_type_to_string(int s) _const_;
 int dhcp6_message_type_from_string(const char *s) _pure_;
+const char *dhcp6_message_status_to_string(int s) _const_;
+int dhcp6_message_status_from_string(const char *s) _pure_;
diff --git a/src/libsystemd-network/dhcp6-protocol.h b/src/libsystemd-network/dhcp6-protocol.h
index c58a07b176..1303a55a82 100644
--- a/src/libsystemd-network/dhcp6-protocol.h
+++ b/src/libsystemd-network/dhcp6-protocol.h
@@ -21,6 +21,9 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <netinet/ip6.h>
+#include <netinet/udp.h>
+
 #include "macro.h"
 #include "sparse-endian.h"
 
@@ -36,6 +39,9 @@ struct DHCP6Message {
 
 typedef struct DHCP6Message DHCP6Message;
 
+#define DHCP6_MIN_OPTIONS_SIZE \
+        1280 - sizeof(struct ip6_hdr) - sizeof(struct udphdr)
+
 #define IN6ADDR_ALL_DHCP6_RELAY_AGENTS_AND_SERVERS_INIT \
         { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
               0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x02 } } }
diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
index 7be64244ad..431801d6f0 100644
--- a/src/libsystemd-network/sd-dhcp6-client.c
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -21,6 +21,7 @@
 
 #include <errno.h>
 #include <string.h>
+#include <sys/ioctl.h>
 
 #include "udev.h"
 #include "udev-util.h"
@@ -33,6 +34,7 @@
 #include "sd-dhcp6-client.h"
 #include "dhcp6-protocol.h"
 #include "dhcp6-internal.h"
+#include "dhcp6-lease-internal.h"
 
 #define SYSTEMD_PEN 43793
 #define HASH_KEY SD_ID128_MAKE(80,11,8c,c2,fe,4a,03,ee,3e,d6,0c,6f,36,39,14,09)
@@ -47,6 +49,7 @@ struct sd_dhcp6_client {
         struct ether_addr mac_addr;
         DHCP6IA ia_na;
         be32_t transaction_id;
+        struct sd_dhcp6_lease *lease;
         int fd;
         sd_event_source *receive_message;
         usec_t retransmit_time;
@@ -81,6 +84,17 @@ const char * dhcp6_message_type_table[_DHCP6_MESSAGE_MAX] = {
 
 DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_type, int);
 
+const char * dhcp6_message_status_table[_DHCP6_STATUS_MAX] = {
+        [DHCP6_STATUS_SUCCESS] = "Success",
+        [DHCP6_STATUS_UNSPEC_FAIL] = "Unspecified failure",
+        [DHCP6_STATUS_NO_ADDRS_AVAIL] = "No addresses available",
+        [DHCP6_STATUS_NO_BINDING] = "Binding unavailable",
+        [DHCP6_STATUS_NOT_ON_LINK] = "Not on link",
+        [DHCP6_STATUS_USE_MULTICAST] = "Use multicast",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_status, int);
+
 int sd_dhcp6_client_set_callback(sd_dhcp6_client *client,
                                  sd_dhcp6_client_cb_t cb, void *userdata)
 {
@@ -377,9 +391,209 @@ static int client_ensure_iaid(sd_dhcp6_client *client) {
         return 0;
 }
 
+static int client_parse_message(sd_dhcp6_client *client,
+                                DHCP6Message *message, size_t len,
+                                sd_dhcp6_lease *lease) {
+        int r;
+        uint8_t *optval, *option = (uint8_t *)(message + 1), *id = NULL;
+        uint16_t optcode, status;
+        size_t optlen, id_len;
+        bool clientid = false;
+        be32_t iaid_lease;
+
+        while ((r = dhcp6_option_parse(&option, &len, &optcode, &optlen,
+                                       &optval)) >= 0) {
+                switch (optcode) {
+                case DHCP6_OPTION_CLIENTID:
+                        if (clientid) {
+                                log_dhcp6_client(client, "%s contains multiple clientids",
+                                                 dhcp6_message_type_to_string(message->type));
+                                return -EINVAL;
+                        }
+
+                        if (optlen != sizeof(client->duid) ||
+                            memcmp(&client->duid, optval, optlen) != 0) {
+                                log_dhcp6_client(client, "%s DUID does not match",
+                                                 dhcp6_message_type_to_string(message->type));
+
+                                return -EINVAL;
+                        }
+                        clientid = true;
+
+                        break;
+
+                case DHCP6_OPTION_SERVERID:
+                        r = dhcp6_lease_get_serverid(lease, &id, &id_len);
+                        if (r >= 0 && id) {
+                                log_dhcp6_client(client, "%s contains multiple serverids",
+                                                 dhcp6_message_type_to_string(message->type));
+                                return -EINVAL;
+                        }
+
+                        r = dhcp6_lease_set_serverid(lease, optval, optlen);
+                        if (r < 0)
+                                return r;
+
+                        break;
+
+                case DHCP6_OPTION_PREFERENCE:
+                        if (optlen != 1)
+                                return -EINVAL;
+
+                        r = dhcp6_lease_set_preference(lease, *optval);
+                        if (r < 0)
+                                return r;
+
+                        break;
+
+                case DHCP6_OPTION_STATUS_CODE:
+                        if (optlen < 2)
+                                return -EINVAL;
+
+                        status = optval[0] << 8 | optval[1];
+                        if (status) {
+                                log_dhcp6_client(client, "%s Status %s",
+                                                 dhcp6_message_type_to_string(message->type),
+                                                 dhcp6_message_status_to_string(status));
+                                return -EINVAL;
+                        }
+
+                        break;
+
+                case DHCP6_OPTION_IA_NA:
+                        r = dhcp6_option_parse_ia(&optval, &optlen, optcode,
+                                                  &lease->ia);
+                        if (r < 0 && r != -ENOMSG)
+                                return r;
+
+                        r = dhcp6_lease_get_iaid(lease, &iaid_lease);
+                        if (r < 0)
+                                return r;
+
+                        if (client->ia_na.id != iaid_lease) {
+                                log_dhcp6_client(client, "%s has wrong IAID",
+                                                 dhcp6_message_type_to_string(message->type));
+                                return -EINVAL;
+                        }
+
+                        break;
+                }
+        }
+
+        if ((r < 0 && r != -ENOMSG) || !clientid) {
+                log_dhcp6_client(client, "%s has incomplete options",
+                                 dhcp6_message_type_to_string(message->type));
+                return -EINVAL;
+        }
+
+        r = dhcp6_lease_get_serverid(lease, &id, &id_len);
+        if (r < 0)
+                log_dhcp6_client(client, "%s has no server id",
+                                 dhcp6_message_type_to_string(message->type));
+
+        return r;
+}
+
+static int client_receive_advertise(sd_dhcp6_client *client,
+                                    DHCP6Message *advertise, size_t len) {
+        int r;
+        _cleanup_dhcp6_lease_free_ sd_dhcp6_lease *lease = NULL;
+        uint8_t pref_advertise = 0, pref_lease = 0;
+
+        if (advertise->type != DHCP6_ADVERTISE)
+                return -EINVAL;
+
+        r = dhcp6_lease_new(&lease);
+        if (r < 0)
+                return r;
+
+        r = client_parse_message(client, advertise, len, lease);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_lease_get_preference(lease, &pref_advertise);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_lease_get_preference(client->lease, &pref_lease);
+        if (!client->lease || r < 0 || pref_advertise > pref_lease) {
+                sd_dhcp6_lease_unref(client->lease);
+                client->lease = lease;
+                lease = NULL;
+                r = 0;
+        }
+
+        return r;
+}
+
 static int client_receive_message(sd_event_source *s, int fd, uint32_t revents,
-                                  void *userdata)
-{
+                                  void *userdata) {
+        sd_dhcp6_client *client = userdata;
+        _cleanup_free_ DHCP6Message *message;
+        int r, buflen, len;
+
+        assert(s);
+        assert(client);
+        assert(client->event);
+
+        r = ioctl(fd, FIONREAD, &buflen);
+        if (r < 0 || buflen <= 0)
+                buflen = DHCP6_MIN_OPTIONS_SIZE;
+
+        message = malloc0(buflen);
+        if (!message)
+                return -ENOMEM;
+
+        len = read(fd, message, buflen);
+        if ((size_t)len < sizeof(DHCP6Message)) {
+                log_dhcp6_client(client, "could not receive message from UDP socket: %s", strerror(errno));
+                return 0;
+        }
+
+        switch(message->type) {
+        case DHCP6_SOLICIT:
+        case DHCP6_REQUEST:
+        case DHCP6_CONFIRM:
+        case DHCP6_RENEW:
+        case DHCP6_REBIND:
+        case DHCP6_RELEASE:
+        case DHCP6_DECLINE:
+        case DHCP6_INFORMATION_REQUEST:
+        case DHCP6_RELAY_FORW:
+        case DHCP6_RELAY_REPL:
+                return 0;
+
+        case DHCP6_ADVERTISE:
+        case DHCP6_REPLY:
+        case DHCP6_RECONFIGURE:
+                break;
+
+        default:
+                log_dhcp6_client(client, "unknown message type %d",
+                                 message->type);
+                return 0;
+        }
+
+        if (client->transaction_id != (message->transaction_id &
+                                       htobe32(0x00ffffff)))
+                return 0;
+
+        switch (client->state) {
+        case DHCP6_STATE_SOLICITATION:
+                r = client_receive_advertise(client, message, len);
+
+                break;
+
+        case DHCP6_STATE_STOPPED:
+        case DHCP6_STATE_RS:
+                return 0;
+        }
+
+        if (r >= 0) {
+                log_dhcp6_client(client, "Recv %s",
+                                 dhcp6_message_type_to_string(message->type));
+        }
+
         return 0;
 }