libsystemd-dhcp: Fix receiving of other message when expecting Ack

When a DHCP Nak is received, return a DHCP_EVENT_NO_LEASE event. If
some other DHCP message is received or an error happens when parsing
options, return -ENOMSG in order to ignore the packet. There may be
more than one server serving the same subnet, each server will send
its Offer to the client.

diff --git a/src/libsystemd-dhcp/dhcp-client.c b/src/libsystemd-dhcp/dhcp-client.c
index 18a6e3c50d725cb93ed06df60cd708267284e9c1..7dc154612816ac3902070cce9bbecdba76efe5f4 100644 (file)
--- a/src/libsystemd-dhcp/dhcp-client.c
+++ b/src/libsystemd-dhcp/dhcp-client.c
@@ -731,8 +731,15 @@ static int client_receive_ack(sd_dhcp_client *client, DHCPPacket *offer,
         len = len - DHCP_IP_UDP_SIZE;
         r = dhcp_option_parse(&offer->dhcp, len, client_parse_offer, lease);
 
-        if (r != DHCP_ACK)
+        if (r == DHCP_NAK) {
+                r = DHCP_EVENT_NO_LEASE;
                 goto error;
+        }
+
+        if (r != DHCP_ACK) {
+                r = -ENOMSG;
+                goto error;
+        }
 
         lease->address = offer->dhcp.yiaddr;