X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=src%2Flibsystemd-dhcp%2Fsd-dhcp-client.c;h=01397cff398be59c3a4e1a1fee05109bf28e7688;hp=350675530466f2f472bcd2a5ab7b5a986de79e33;hb=0a1b6da82109c3b08b1f966a1625a77cc312135a;hpb=ee57a737a5b72bc3f3f46aafd2bbc452b61dcaa7

diff --git a/src/libsystemd-dhcp/sd-dhcp-client.c b/src/libsystemd-dhcp/sd-dhcp-client.c
index 350675530..01397cff3 100644
--- a/src/libsystemd-dhcp/sd-dhcp-client.c
+++ b/src/libsystemd-dhcp/sd-dhcp-client.c
@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <net/ethernet.h>
 #include <sys/param.h>
+#include <sys/ioctl.h>
 
 #include "util.h"
 #include "list.h"
@@ -205,11 +206,17 @@ static int client_message_init(sd_dhcp_client *client, DHCPMessage *message,
                                size_t *optlen) {
         int r;
 
-        r = dhcp_message_init(message, BOOTREQUEST, client->xid, type,
-                              secs, opt, optlen);
+        assert(secs);
+
+        r = dhcp_message_init(message, BOOTREQUEST, client->xid, type, opt,
+                              optlen);
         if (r < 0)
                 return r;
 
+        /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
+           refuse to issue an DHCP lease if 'secs' is set to zero */
+        message->secs = htobe16(secs);
+
         memcpy(&message->chaddr, &client->mac_addr, ETH_ALEN);
 
         if (client->state == DHCP_STATE_RENEWING ||
@@ -279,7 +286,7 @@ static int client_send_discover(sd_dhcp_client *client, uint16_t secs) {
         if (err < 0)
                 return err;
 
-        dhcp_packet_append_ip_headers(discover, BOOTREQUEST, len);
+        dhcp_packet_append_ip_headers(discover, len);
 
         err = dhcp_network_send_raw_socket(client->fd, &client->link,
                                            discover, len);
@@ -332,7 +339,7 @@ static int client_send_request(sd_dhcp_client *client, uint16_t secs) {
                                                    &request->dhcp,
                                                    len - DHCP_IP_UDP_SIZE);
         } else {
-                dhcp_packet_append_ip_headers(request, BOOTREQUEST, len);
+                dhcp_packet_append_ip_headers(request, len);
 
                 err = dhcp_network_send_raw_socket(client->fd, &client->link,
                                                    request, len);
@@ -736,12 +743,30 @@ static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message,
         assert(client->event);
         assert(message);
 
-        if (be32toh(message->xid) != client->xid)
+        if (len < DHCP_MESSAGE_SIZE) {
+                log_dhcp_client(client, "message too small (%d bytes): "
+                                "ignoring", len);
+                return 0;
+        }
+
+        if (message->op != BOOTREPLY) {
+                log_dhcp_client(client, "not a BOOTREPLY message: ignoring");
                 return 0;
+        }
+
+        if (be32toh(message->xid) != client->xid) {
+                log_dhcp_client(client, "received xid (%u) does not match "
+                                "expected (%u): ignoring",
+                                be32toh(message->xid), client->xid);
+                return 0;
+        }
 
         if (memcmp(&message->chaddr[0], &client->mac_addr.ether_addr_octet,
-                   ETHER_ADDR_LEN))
+                   ETHER_ADDR_LEN)) {
+                log_dhcp_client(client, "received chaddr does not match "
+                                "expected: ignoring");
                 return 0;
+        }
 
         switch (client->state) {
         case DHCP_STATE_SELECTING:
@@ -829,16 +854,23 @@ error:
 static int client_receive_message_udp(sd_event_source *s, int fd,
                                       uint32_t revents, void *userdata) {
         sd_dhcp_client *client = userdata;
-        uint8_t buf[sizeof(DHCPMessage) + DHCP_MIN_OPTIONS_SIZE];
-        int buflen = sizeof(buf);
-        int len, r = 0;
+        _cleanup_free_ DHCPMessage *message = NULL;
+        int buflen = 0, len, r;
         usec_t time_now;
 
         assert(s);
         assert(client);
         assert(client->event);
 
-        len = read(fd, &buf, buflen);
+        r = ioctl(fd, FIONREAD, &buflen);
+        if (r < 0 || buflen <= 0)
+                buflen = sizeof(DHCPMessage) + DHCP_MIN_OPTIONS_SIZE;
+
+        message = malloc0(buflen);
+        if (!message)
+                return -ENOMEM;
+
+        len = read(fd, message, buflen);
         if (len < 0)
                 return 0;
 
@@ -846,34 +878,36 @@ static int client_receive_message_udp(sd_event_source *s, int fd,
         if (r < 0)
                 return client_stop(client, r);
 
-        return client_handle_message(client, (DHCPMessage *) buf, len,
+        return client_handle_message(client, message, len,
                                      time_now);
 }
 
 static int client_receive_message_raw(sd_event_source *s, int fd,
                                       uint32_t revents, void *userdata) {
         sd_dhcp_client *client = userdata;
-        uint8_t buf[sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE];
-        int buflen = sizeof(buf);
-        int len, r = 0;
-        DHCPPacket *packet;
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        int buflen = 0, len, r;
         usec_t time_now;
 
         assert(s);
         assert(client);
         assert(client->event);
 
-        len = read(fd, &buf, buflen);
+        r = ioctl(fd, FIONREAD, &buflen);
+        if (r < 0 || buflen <= 0)
+                buflen = sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE;
+
+        packet = malloc0(buflen);
+        if (!packet)
+                return -ENOMEM;
+
+        len = read(fd, packet, buflen);
         if (len < 0)
                 return 0;
 
-        packet = (DHCPPacket *) buf;
-
-        r = dhcp_packet_verify_headers(packet, BOOTREPLY, len);
-        if (r < 0) {
-                log_dhcp_client(client, "ignoring DHCP packet with invalid headers");
+        r = dhcp_packet_verify_headers(packet, len);
+        if (r < 0)
                 return 0;
-        }
 
         len -= DHCP_IP_UDP_SIZE;