common/parsing_helpers.h: Fix sizeof checks to use pointer target

Marcus noticed that there was a sizeof() check in parsing_helpers that was
using the size of the pointer, not of the struct being pointed to. Turns
out there were two of these, so let's fix both.

Fixes #199.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>

Author: tohojo

common/parsing_helpers.h

@@ -160,7 +160,7 @@ static __always_inline int parse_iphdr(struct hdr_cursor *nh,
 
 	hdrsize = iph->ihl * 4;
 	/* Sanity check packet field is valid */
-	if(hdrsize < sizeof(iph))
+	if(hdrsize < sizeof(*iph))
 		return -1;
 
 	/* Variable-length IPv4 header, need to use byte-based arithmetic */
@@ -256,7 +256,7 @@ static __always_inline int parse_tcphdr(struct hdr_cursor *nh,
 
 	len = h->doff * 4;
 	/* Sanity check packet field is valid */
-	if(len < sizeof(h))
+	if(len < sizeof(*h))
 		return -1;
 
 	/* Variable-length TCP header, need to use byte-based arithmetic */