Changeset 15749d5 for lib/protocols_transport.c

Timestamp:

09/27/10 14:01:58 (11 years ago)

Author:

Shane Alcock <salcock@…>

Branches:

4.0.1-hotfixes, cachetimestamps, develop, dpdk-ndag, etsilive, getfragoff, help, libtrace4, master, ndag_format, pfring, rc-4.0.1, rc-4.0.2, rc-4.0.3, rc-4.0.4, ringdecrementfix, ringperformance, ringtimestampfixes

Children:

7e8a25a

Parents:

5d081ff

Message:

Added a trace_get_payload_length() function which returns the original payload length for a packet - got sick of re-implementing this function everytime I wanted to know the size of the application payload.

This function currently works for TCP, UDP and ICMP packets. All other protocols
will return 0.

File:

• lib/protocols_transport.c (modified) (1 diff)

lib/protocols_transport.c

@@ -47 +47 @@
  *      ICMP
  */
+
+/* Get the size of the payload as it was in the original packet, i.e. prior
+ * to any truncation.
+ *
+ * Basically, wire length minus the packet headers.
+ *
+ * Currently only supports IP (v4 and v6) and TCP, UDP and ICMP. Will return
+ * 0 if an unsupported protocol header is encountered, or if one of the 
+ * headers is truncated.
+ */
+DLLEXPORT size_t trace_get_payload_length(const libtrace_packet_t *packet) {
+
+        void *layer;
+        uint16_t ethertype;
+        uint8_t proto;
+        uint32_t rem;
+        libtrace_ip_t *ip;
+        libtrace_ip6_t *ip6;
+        libtrace_tcp_t *tcp;
+        size_t len = 0;
+
+        layer = trace_get_layer3(packet, &ethertype, &rem);
+
+        if (!layer)
+                return 0;
+        switch (ethertype) {
+                case TRACE_ETHERTYPE_IP:
+                        ip = (libtrace_ip_t *)layer;
+                        if (rem < sizeof(libtrace_ip_t))
+                                return 0;
+                        len = ntohs(ip->ip_len) - (4 * ip->ip_hl);
+                        break;
+                case TRACE_ETHERTYPE_IPV6:
+                        ip6 = (libtrace_ip6_t *)layer;
+                        if (rem < sizeof(libtrace_ip6_t))
+                                return 0;
+                        len = ntohs(ip6->plen);
+                        break;
+                default:
+                        return 0;
+        }
+
+        layer = trace_get_transport(packet, &proto, &rem);
+        if (!layer)
+                return 0;
+        
+        switch(proto) {
+                case TRACE_IPPROTO_TCP:
+                        tcp = (libtrace_tcp_t *)layer;
+                        len -= (4 * tcp->doff);
+                        break;
+                case TRACE_IPPROTO_UDP:
+                        len -= sizeof(libtrace_udp_t);
+                        break;
+                case TRACE_IPPROTO_ICMP:
+                        len -= sizeof(libtrace_icmp_t);
+                        break;
+                default:
+                        return 0;
+        }
+
+        return len;
+
+}
 
 DLLEXPORT void *trace_get_transport(const libtrace_packet_t *packet,