dhcp: Process DHCP Ack/Nak message

Process a DHCP Ack/Nak in much the same way as an DHCP Offer. Factor
out header verification and process options sent. Add notification
functionality with discrete values for the outcome of the DHCP Ack/
Nak processing.

2 files changed, 122 insertions, 26 deletions

diff --git a/src/libsystemd-dhcp/dhcp-client.c b/src/libsystemd-dhcp/dhcp-client.c
index b1bdd38593..a15866932c 100644
--- a/src/libsystemd-dhcp/dhcp-client.c
+++ b/src/libsystemd-dhcp/dhcp-client.c
@@ -137,6 +137,11 @@ int sd_dhcp_client_set_mac(sd_dhcp_client *client,
         return 0;
 }
 
+static int client_notify(sd_dhcp_client *client, int event)
+{
+        return 0;
+}
+
 static int client_stop(sd_dhcp_client *client, int error)
 {
         assert_return(client, -EINVAL);
@@ -158,6 +163,7 @@ static int client_stop(sd_dhcp_client *client, int error)
 
         case DHCP_STATE_INIT:
         case DHCP_STATE_SELECTING:
+        case DHCP_STATE_REQUESTING:
 
                 client->start_time = 0;
                 client->state = DHCP_STATE_INIT;
@@ -165,7 +171,6 @@ static int client_stop(sd_dhcp_client *client, int error)
 
         case DHCP_STATE_INIT_REBOOT:
         case DHCP_STATE_REBOOTING:
-        case DHCP_STATE_REQUESTING:
         case DHCP_STATE_BOUND:
         case DHCP_STATE_RENEWING:
         case DHCP_STATE_REBINDING:
@@ -481,41 +486,53 @@ static int client_parse_offer(uint8_t code, uint8_t len, const uint8_t *option,
         return 0;
 }
 
-static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
-                                size_t len)
+static int client_verify_headers(sd_dhcp_client *client, DHCPPacket *message,
+                                 size_t len)
 {
         size_t hdrlen;
-        DHCPLease *lease;
 
         if (len < (DHCP_IP_UDP_SIZE + DHCP_MESSAGE_SIZE))
                 return -EINVAL;
 
-        hdrlen = offer->ip.ihl * 4;
-        if (hdrlen < 20 || hdrlen > len || client_checksum(&offer->ip,
+        hdrlen = message->ip.ihl * 4;
+        if (hdrlen < 20 || hdrlen > len || client_checksum(&message->ip,
                                                            hdrlen))
                 return -EINVAL;
 
-        offer->ip.check = offer->udp.len;
-        offer->ip.ttl = 0;
+        message->ip.check = message->udp.len;
+        message->ip.ttl = 0;
 
-        if (hdrlen + be16toh(offer->udp.len) > len ||
-            client_checksum(&offer->ip.ttl, be16toh(offer->udp.len) + 12))
+        if (hdrlen + be16toh(message->udp.len) > len ||
+            client_checksum(&message->ip.ttl, be16toh(message->udp.len) + 12))
                 return -EINVAL;
 
-        if (be16toh(offer->udp.source) != DHCP_PORT_SERVER ||
-            be16toh(offer->udp.dest) != DHCP_PORT_CLIENT)
+        if (be16toh(message->udp.source) != DHCP_PORT_SERVER ||
+            be16toh(message->udp.dest) != DHCP_PORT_CLIENT)
                 return -EINVAL;
 
-        if (offer->dhcp.op != BOOTREPLY)
+        if (message->dhcp.op != BOOTREPLY)
                 return -EINVAL;
 
-        if (be32toh(offer->dhcp.xid) != client->xid)
+        if (be32toh(message->dhcp.xid) != client->xid)
                 return -EINVAL;
 
-        if (memcmp(&offer->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
+        if (memcmp(&message->dhcp.chaddr[0], &client->mac_addr.ether_addr_octet,
                     ETHER_ADDR_LEN))
                 return -EINVAL;
 
+        return 0;
+}
+
+static int client_receive_offer(sd_dhcp_client *client, DHCPPacket *offer,
+                                size_t len)
+{
+        int err;
+        DHCPLease *lease;
+
+        err = client_verify_headers(client, offer, len);
+        if (err < 0)
+                return err;
+
         lease = new0(DHCPLease, 1);
         if (!lease)
                 return -ENOMEM;
@@ -543,13 +560,63 @@ error:
         return -ENOMSG;
 }
 
+static int client_receive_ack(sd_dhcp_client *client, DHCPPacket *offer,
+                              size_t len)
+{
+        int r;
+        DHCPLease *lease;
+
+        r = client_verify_headers(client, offer, len);
+        if (r < 0)
+                return r;
+
+        lease = new0(DHCPLease, 1);
+        if (!lease)
+                return -ENOBUFS;
+
+        len = len - DHCP_IP_UDP_SIZE;
+        r = dhcp_option_parse(&offer->dhcp, len, client_parse_offer, lease);
+
+        if (r != DHCP_ACK)
+                goto error;
+
+        lease->address = offer->dhcp.yiaddr;
+
+        if (lease->address == INADDR_ANY ||
+            lease->server_address == INADDR_ANY ||
+            lease->subnet_mask == INADDR_ANY || lease->lifetime == 0) {
+                r = -ENOMSG;
+                goto error;
+        }
+
+        r = DHCP_EVENT_IP_ACQUIRE;
+        if (client->lease) {
+                if (client->lease->address != lease->address ||
+                    client->lease->subnet_mask != lease->subnet_mask ||
+                    client->lease->router != lease->router) {
+                        r = DHCP_EVENT_IP_CHANGE;
+                }
+
+                free(client->lease);
+        }
+
+        client->lease = lease;
+
+        return r;
+
+error:
+        free(lease);
+
+        return r;
+}
+
 static int client_receive_raw_message(sd_event_source *s, int fd,
                                       uint32_t revents, void *userdata)
 {
         sd_dhcp_client *client = userdata;
         uint8_t buf[sizeof(DHCPPacket) + DHCP_CLIENT_MIN_OPTIONS_SIZE];
         int buflen = sizeof(buf);
-        int len, err = 0;
+        int len, r = 0;
         DHCPPacket *message;
         usec_t time_now;
 
@@ -557,8 +624,8 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
         if (len < 0)
                 return 0;
 
-        err = sd_event_get_now_monotonic(client->event, &time_now);
-        if (err < 0)
+        r = sd_event_get_now_monotonic(client->event, &time_now);
+        if (r < 0)
                 goto error;
 
         message = (DHCPPacket *)&buf;
@@ -574,20 +641,43 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
                         client->state = DHCP_STATE_REQUESTING;
                         client->attempt = 1;
 
-                        err = sd_event_add_monotonic(client->event, time_now, 0,
-                                                     client_timeout_resend,
-                                                     client,
-                                                     &client->timeout_resend);
-                        if (err < 0)
+                        r = sd_event_add_monotonic(client->event, time_now, 0,
+                                                   client_timeout_resend,
+                                                   client,
+                                                   &client->timeout_resend);
+                        if (r < 0)
                                 goto error;
                 }
 
                 break;
 
+        case DHCP_STATE_REQUESTING:
+
+                r = client_receive_ack(client, message, len);
+                if (r == DHCP_EVENT_NO_LEASE)
+                        goto error;
+
+                if (r >= 0) {
+                        client->timeout_resend =
+                                sd_event_source_unref(client->timeout_resend);
+
+                        client->state = DHCP_STATE_BOUND;
+                        client->attempt = 1;
+
+                        client->last_addr = client->lease->address;
+
+                        client_notify(client, DHCP_EVENT_IP_ACQUIRE);
+
+                        close(client->fd);
+                        client->fd = -1;
+                        client->receive_message =
+                                sd_event_source_unref(client->receive_message);
+                }
+                break;
+
         case DHCP_STATE_INIT:
         case DHCP_STATE_INIT_REBOOT:
         case DHCP_STATE_REBOOTING:
-        case DHCP_STATE_REQUESTING:
         case DHCP_STATE_BOUND:
         case DHCP_STATE_RENEWING:
         case DHCP_STATE_REBINDING:
@@ -596,8 +686,8 @@ static int client_receive_raw_message(sd_event_source *s, int fd,
         }
 
 error:
-        if (err < 0)
-                return client_stop(client, err);
+        if (r < 0)
+                return client_stop(client, r);
 
         return 0;
 }
diff --git a/src/systemd/sd-dhcp-client.h b/src/systemd/sd-dhcp-client.h
index 5c9c32793e..ed72cf1a7e 100644
--- a/src/systemd/sd-dhcp-client.h
+++ b/src/systemd/sd-dhcp-client.h
@@ -27,6 +27,12 @@
 
 #include "sd-event.h"
 
+enum {
+        DHCP_EVENT_NO_LEASE                     = 1,
+        DHCP_EVENT_IP_ACQUIRE                   = 2,
+        DHCP_EVENT_IP_CHANGE                    = 3,
+};
+
 typedef struct sd_dhcp_client sd_dhcp_client;
 
 int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option);