struct packet *udp6Reply(struct packet *m0)
{
ethdr *eh;
ip6hdr *ip;
udphdr *ui;
struct packet *m;
m = new_pkt(m0->len);
if (m == NULL)
return NULL;
copy_pkt(m, m0);
eh = (ethdr *)(m->data);
ip = (ip6hdr *)(eh + 1);
ui = (udphdr *)(ip + 1);
swap_ehead(m->data);
swap_ip6head(m);
ip->ip6_hlim = TTL;
ui->sport ^= ui->dport;
ui->dport ^= ui->sport;
ui->sport ^= ui->dport;
ui->cksum = 0;
ui->cksum = cksum6(ip, IPPROTO_UDP, ntohs(ui->len));
return m;
}
/**
* @brief Feed a list packets into an eBPF program.
* @details This is a mock function emulating the behavior of a running
* eBPF program. It takes a list of input packets and iteratively parses them
* using the given imported ebpf_filter function. The output defines whether
* or not the packet is "dropped." If the packet is not dropped, its content is
* copied and appended to an output packet list.
*
* @param pkt_list A list of input packets running through the filter.
* @return The list of packets "surviving" the filter function
*/
pcap_list_t *feed_packets(packet_filter ebpf_filter, pcap_list_t *pkt_list, int debug) {
pcap_list_t *output_pkts = allocate_pkt_list();
uint32_t list_len = get_pkt_list_length(pkt_list);
for (uint32_t i = 0; i < list_len; i++) {
/* Parse each packet in the list and check the result */
struct sk_buff skb;
pcap_pkt *input_pkt = get_packet(pkt_list, i);
skb.data = (void *) input_pkt->data;
skb.len = input_pkt->pcap_hdr.len;
int result = ebpf_filter(&skb);
if (result != 0) {
/* We copy the entire content to emulate an outgoing packet */
pcap_pkt *out_pkt = copy_pkt(input_pkt);
output_pkts = append_packet(output_pkts, out_pkt);
}
if (debug)
printf("Result of the eBPF parsing is: %d\n", result);
}
return output_pkts;
}
void
test_case(uint16_t payload_sz, uint8_t *ip_opt, int ip_opt_size, custom_opt_t *opt,
uint16_t expected_opt_len)
{
pkt_t *pkt;
error_t err;
ip_t *new_ip;
ip_t *ip;
uint16_t new_hdr_len;
int res;
uint16_t old_csum;
uint16_t old_len;
uint16_t old_hdr_len;
uint16_t new_len;
pkt_t *copy;
uint8_t *pay1, *pay2;
LOG("Test case : creating packet, appending IP option\n");
pkt = create_pkt(payload_sz, ip_opt, ip_opt_size);
ip = (ip_t *)pkt->msg;
old_hdr_len = ip->ip_hl * 4;
old_csum = ip->ip_sum;
old_len = ntohs(ip->ip_len);
copy = copy_pkt(pkt);
res = ip_add_custom_option(pkt, opt, &err);
if (res) {
LOG_ERR("Test Case failed with %d\n", res);
free(pkt);
return;
}
LOG("Test case : checking new header len\n");
new_ip = (ip_t *)pkt->msg;
new_hdr_len = new_ip->ip_hl * 4;
LOG("New hdr len : %d\n", new_hdr_len);
if (new_hdr_len <= MIN_IP_SIZE) {
LOG_ERR("Test Case failed, expecting bigger header size");
LOG_ERR("Recieved header size %d\n", new_hdr_len);
free(pkt);
return;
}
LOG("Test case : testing new packet len\n");
new_len = payload_sz + MIN_IP_SIZE + expected_opt_len;
if (ntohs(new_ip->ip_len) != new_len) {
LOG_ERR("Test case failed, incorrect packet len\n");
LOG_ERR("Expected %d, Recvd %d\n", new_len, ntohs(new_ip->ip_len));
free(pkt);
return;
}
LOG("Test case : checking ip checksum\n");
if (old_csum == new_ip->ip_sum) {
LOG_ERR("Test case failed, expecting a different checksum\n");
free(pkt);
return;
}
LOG("Test case : comparing payload\n");
pay1 = (uint8_t *)copy->msg + MIN_IP_SIZE + ip_opt_size;
pay2 = (uint8_t *)new_ip + new_hdr_len;
if (compare_payload(pay1, pay2, payload_sz)) {
LOG_ERR("Test case failed, payloads didn't match\n");
free(pkt);
return;
}
LOG("Test case : remove option\n");
res = ip_remove_custom_option(pkt, opt, &err);
if (res) {
LOG_ERR("Test case failed, remove option failed with %d\n", res);
free(pkt);
return;
}
LOG("Test case : comparing packet len after removing options\n");
new_ip = (ip_t *)pkt->msg;
new_hdr_len = new_ip->ip_hl * 4;
if (ntohs(new_ip->ip_len) != copy->len) {
LOG_ERR("Test case failed, recvd len (%d), expected (%d)\n",
pkt->len, copy->len);
free(pkt);
return;
}
LOG("Test case : comparing packet contents after removing options\n");
pay1 = (uint8_t *)copy->msg + MIN_IP_SIZE + ip_opt_size;
pay2 = (uint8_t *)new_ip + new_hdr_len;
if (memcmp(pay1, pay2, payload_sz)) {
LOG_ERR("Test case failed, contents didn't match\n");
free(pkt);
return;
}
free(pkt);
}
