From d62be280a151883866554e9ea00a5efed2fa593a Mon Sep 17 00:00:00 2001 From: Mosder Date: Wed, 17 Jun 2026 22:55:55 +0200 Subject: feat: added simple reading of packets from file and printing the payloads. TODO: utilize TCP sequence number to make sure the stream is read in order and parse the packets without reassemblying the entire stream (which might be enormous), but keeping in mind that entire fight result might be accross multiple segments --- analyzer/utils/pcap.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) create mode 100644 analyzer/utils/pcap.c (limited to 'analyzer/utils/pcap.c') diff --git a/analyzer/utils/pcap.c b/analyzer/utils/pcap.c new file mode 100644 index 0000000..cdefba7 --- /dev/null +++ b/analyzer/utils/pcap.c @@ -0,0 +1,36 @@ +#include "pcap.h" + +#include +#include +#include + +const unsigned char *get_payload_from_packet(const unsigned char *packet, const struct pcap_pkthdr *packet_data, int *payload_len) { + // get Ethernet header + const struct ether_header *eth_header = (const struct ether_header *)packet; + int eth_header_len = sizeof(struct ether_header); + + // check if it's IP + if (ntohs(eth_header->ether_type) != ETHERTYPE_IP) { + *payload_len = -1; + return NULL; + } + + // get IP header + const struct ip *ip_header = (const struct ip *)(packet + eth_header_len); + int ip_header_len = ip_header->ip_hl * 4; + + // check if it's TCP + if (ip_header->ip_p != IPPROTO_TCP) { + *payload_len = -1; + return NULL; + } + + // get TCP header + const struct tcphdr *tcp_header = (const struct tcphdr *)(packet + eth_header_len + ip_header_len); + int tcp_header_len = tcp_header->th_off * 4; + + // get payload + int total_header_len = eth_header_len + ip_header_len + tcp_header_len; + *payload_len = packet_data->caplen - total_header_len; + return packet + total_header_len; +} -- cgit v1.2.3