DHCP: Give a better message when packet validation failes

We return ERANGE for underflow and ENOBUFS for overflow,
but these error strings could be misleading.
For EINVAL report invalid checksum, otherwise invalid UDP packet.

diff --git a/src/dhcp.c b/src/dhcp.c
index eafd6e7aa49967f97d438ad8a98e19e156c5b48f..ac52382424266a8a40afc062f6d8a088ee26e3f8 100644 (file)
--- a/src/dhcp.c
+++ b/src/dhcp.c
@@ -3338,12 +3338,13 @@ dhcp_handlepacket(struct interface *ifp, uint8_t *data, size_t len)
        const struct dhcp_state *state = D_CSTATE(ifp);
 
        if (valid_udp_packet(data, len, &from, state->bpf_flags) == -1) {
+               const char *errstr;
+
                if (errno == EINVAL)
-                       logerrx("%s: checksum failure from %s",
-                         ifp->name, inet_ntoa(from));
+                       errstr = "checksum failure";
                else
-                       logerr("%s: invalid UDP packet from %s",
-                         ifp->name, inet_ntoa(from));
+                       errstr = "invalid UDP packet";
+               logerrx("%s: %s from %s", errstr, ifp->name, inet_ntoa(from));
                return;
        }