Use GNU TCP/UDP header definitions to have access to _GNU_SOURCE func…

…tions

The code currently assumes to have path names with limited length. This seems
to cause crashes and thus these static allocations will be replaced with
asprintf to avoid buffer overflows by str* functions. Unfortunately, the change
to _GNU_SOURCE also changes the definiton of the struct tcphdr and udphdr.

SConstruct

@@ -1,5 +1,5 @@
 #!/usr/bin/evn python
-env = Environment(CCFLAGS='-Wall -g')
+env = Environment(CCFLAGS='-Wall -g', CPPFLAGS='-D_GNU_SOURCE')
 lib_path = ['/usr/local/lib', '/usr/lib']
 libs = Glob('./*.a') + ['pcap']
 cpp_path=['.']

pkt2flow.c

@@ -29,7 +29,6 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  */
-#define _BSD_SOURCE
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -227,15 +226,15 @@ static void process_trace(void)
 			if (hdr.caplen < offset + sizeof(struct tcphdr))
 				continue;
 			tcph = (struct tcphdr *)(pkt + offset);
-			src_port = ntohs(tcph->th_sport);
-			dst_port = ntohs(tcph->th_dport);
+			src_port = ntohs(tcph->source);
+			dst_port = ntohs(tcph->dest);
 			break;
 		case IPPROTO_UDP:
 			if (hdr.caplen < offset + sizeof(struct udphdr))
 				continue;
 			udph = (struct udphdr *)(pkt + offset);
-			src_port = ntohs(udph->uh_sport);
-			dst_port = ntohs(udph->uh_dport);
+			src_port = ntohs(udph->source);
+			dst_port = ntohs(udph->dest);
 			break;
 		default:
 			src_port = 0;
@@ -247,8 +246,7 @@ static void process_trace(void)
 		pair = find_ip_pair(iph->ip_src.s_addr, iph->ip_dst.s_addr,
 				    src_port, dst_port);
 		if (pair == NULL) {
-			if ((iph->ip_p == IPPROTO_TCP) &&
-			    ((tcph->th_flags & TH_SYN) != TH_SYN) &&
+			if ((iph->ip_p == IPPROTO_TCP) && !tcph->syn &&
 			    !isset_bits(dump_allowed, DUMP_TCP_NOSYN_ALLOWED)) {
 				// No SYN detected and don't create a new flow
 				continue;
@@ -258,7 +256,7 @@ static void process_trace(void)
 						dst_port);
 			switch (iph->ip_p) {
 			case IPPROTO_TCP:
-				if ((tcph->th_flags & TH_SYN) == TH_SYN)
+				if (tcph->syn)
 					pair->pdf.status = STS_TCP_SYN;
 				else
 					pair->pdf.status = STS_TCP_NOSYN;