]> sjero.net Git - ltp2tcp/blobdiff - encap.c
projects / ltp2tcp / blobdiff
? search:
summary | shortlog | log | commit | commitdiff | tree
raw | inline | side by side
Checksum Computation!!
[ltp2tcp] / encap.c
diff --git a/encap.c b/encap.c
index 51d236784a59af47e758d8c91861ecbac33b6f7c..c841ba29e5d76098a67f3bf2b26af1626a22b4a4 100644 (file)
--- a/encap.c
+++ b/encap.c
@@ -1,12 +1,34 @@
 /******************************************************************************
-Author: Samuel Jero
+Utility to convert a LTP flow to a TCP flow for LTP analysis via tcptrace.
+Utility Functions for Encapsulation
 
-Date: 12/2010
+Copyright (C) 2013  Samuel Jero <sj323707@ohio.edu>
 
-Description:  Utility Functions for Encapsulation
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
 
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Author: Samuel Jero <sj323707@ohio.edu>
+Date: 06/2013
+
+Notes:
+       1)Only handles one LTP "connection". There isn't a good way to separate
+               different LTP "connections" from new sessions of the same "connection".
+               Use Tcpdump filters to separate connections. Libpcap filtering could also
+               be added in ltp2tcp.
+       2)Uses some special types from Linux (u_char, u_int32_t)
 ******************************************************************************/
 #include "ltp2tcp.h"
+#include "checksums.h"
 
 
 
@@ -53,6 +75,7 @@ int fill_eip4_encap(struct eip4_en_p *eip, const u_char* data, int dlen, struct
 /* encapsulation manipulation after conversion */
 int eip4_post(struct eip4_en_p *eip, int tlen, u_char* data){
        struct iphdr *iph;
+       struct tcphdr *tcph;
 
        /* Move data pointer to start of IPv4 header*/
        data+=sizeof(struct ether_header);
@@ -65,7 +88,17 @@ int eip4_post(struct eip4_en_p *eip, int tlen, u_char* data){
 
        /*Adjust IPv4 header to account for packet's total length*/
        iph=(struct iphdr*)data;
-       iph->tot_len=htons(sizeof(struct iphdr)+tlen);
+       iph->tot_len=htons(iph->ihl*4+tlen);
+
+       /*Compute IPv4 Checksum*/
+       iph->check=0;
+       iph->check=ipv4_chksum(data,iph->ihl*4);
+
+       /*Compute TCP Checksum*/
+       data+=iph->ihl*4;
+       tcph=(struct tcphdr*)data;
+       tcph->check=0;
+       tcph->check=ipv4_pseudohdr_chksum(data, tlen, (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
        return 0;
 }
 
@@ -114,6 +147,10 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                iph->check=htonl(0);
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr)+4);
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -140,6 +177,11 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                ptr++;
                *ptr=2;
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,tcph->doff*4,
+                                                                               (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /*Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
 
@@ -167,6 +209,10 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                iph->daddr=temp;
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr)+4);
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -193,6 +239,11 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                ptr++;
                *ptr=2;
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,tcph->doff*4 ,
+                                                                       (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /*Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
 
@@ -216,6 +267,10 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                iph->check=htonl(0);
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr));
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -236,6 +291,11 @@ int eip4_handshake(struct eip4_en_p *eip, struct pcap_pkthdr *h){
                tcph->ack_seq=htonl(state.ack_num);
                tcph->window=htons(WIN_FACTOR);
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,tcph->doff*4,
+                                                               (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /*Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
        return 0;
@@ -286,6 +346,10 @@ int eip4_fin(struct eip4_en_p *eip){
                iph->check=htonl(0);
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr));
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -309,6 +373,11 @@ int eip4_fin(struct eip4_en_p *eip){
                /*Update Sequence Number to include the fin packet in the sequence number space*/
                state.seq_num++;
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,tcph->doff*4,
+                                                               (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /* Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
 
@@ -335,6 +404,10 @@ int eip4_fin(struct eip4_en_p *eip){
                iph->daddr=temp;
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr));
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -355,6 +428,11 @@ int eip4_fin(struct eip4_en_p *eip){
                tcph->ack_seq=htonl(state.seq_num);
                tcph->window=htons(WIN_FACTOR);
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,sizeof(struct tcphdr),
+                                                               (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /*Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
 
@@ -378,6 +456,10 @@ int eip4_fin(struct eip4_en_p *eip){
                iph->check=htonl(0);
                iph->tot_len=htons(sizeof(struct iphdr)+sizeof(struct tcphdr));
 
+               /*Compute IPv4 Checksum*/
+               iph->check=0;
+               iph->check=ipv4_chksum((u_char*)iph,iph->ihl*4);
+
                /*Build TCP header*/
                ptr+=sizeof(struct ether_header)+ sizeof(struct iphdr);
                tcph=(struct tcphdr*)ptr;
@@ -398,6 +480,11 @@ int eip4_fin(struct eip4_en_p *eip){
                tcph->ack_seq=htonl(state.ack_num);
                tcph->window=htons(WIN_FACTOR);
 
+               /*Compute TCP Checksum*/
+               tcph->check=0;
+               tcph->check=ipv4_pseudohdr_chksum((u_char*)tcph,tcph->doff*4,
+                                                               (u_char*)&iph->daddr, (u_char*)&iph->saddr, iph->protocol);
+
                /*Save To Packet Capture*/
                pcap_dump((u_char*)state.out,&nh, data);
        return 0;
A utility to convert LTP (RFC5326) packet captures to TCP captures for analysis with tcptrace. Clone using: git clone http://sjero.net/src/ltp2tcp/ ltp2tcp