Hijacking DNS-Traffic works as expected.

Next milestone: responding to .gnunet

diff --git a/src/vpn/gnunet-daemon-vpn.c b/src/vpn/gnunet-daemon-vpn.c
index 27dbe92ae1a8f22600ed24c19fca1954b973118e..1c30e965a5efcc6238a1d39a104ed79c564acc14 100644 (file)
--- a/src/vpn/gnunet-daemon-vpn.c
+++ b/src/vpn/gnunet-daemon-vpn.c
@@ -127,9 +127,72 @@ static void helper_read(void* cls, const struct GNUNET_SCHEDULER_TaskContext* ts
        GNUNET_SCHEDULER_add_read_file (mycls.sched, GNUNET_TIME_UNIT_FOREVER_REL, mycls.fh_from_helper, &helper_read, NULL);
 }
 
+static uint16_t calculate_ip_checksum(uint16_t* hdr, short len) {
+       uint32_t sum = 0;
+       for(; len >= 2; len -= 2)
+               sum += *(hdr++);
+       if (len == 1)
+               sum += *((unsigned char*)hdr);
+
+       sum = (sum >> 16) + (sum & 0xFFFF);
+
+       return ~sum;
+}
+
 static void helper_write(void* cls, const struct GNUNET_SCHEDULER_TaskContext* tsdkctx) {
        if (tsdkctx->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN)
                return;
+       struct answer_packet_list* ans = mycls.answer_head;
+       size_t len = ntohs(ans->pkt.hdr.size);
+
+       size_t data_len = len - sizeof(struct answer_packet) + 1;
+       size_t net_len = sizeof(struct ip_hdr) + sizeof(struct udp_dns) + data_len;
+       size_t pkt_len = sizeof(struct GNUNET_MessageHeader) + sizeof(struct pkt_tun) + net_len;
+
+       struct ip_udp_dns* pkt = alloca(pkt_len);
+
+       pkt->shdr.size = htons(pkt_len);
+       pkt->shdr.type = htons(GNUNET_MESSAGE_TYPE_VPN_HELPER);
+
+       pkt->tun.flags = 0;
+       pkt->tun.type = htons(0x0800);
+
+       pkt->ip_hdr.version = 4;
+       pkt->ip_hdr.hdr_lngth = 5;
+       pkt->ip_hdr.diff_serv = 0;
+       pkt->ip_hdr.tot_lngth = htons(net_len);
+       pkt->ip_hdr.ident = 0;
+       pkt->ip_hdr.flags = 0;
+       pkt->ip_hdr.frag_off = 0;
+       pkt->ip_hdr.ttl = 255;
+       pkt->ip_hdr.proto = 0x11; /* UDP */
+       pkt->ip_hdr.chks = 0; /* Will be calculated later*/
+       pkt->ip_hdr.sadr = ans->pkt.from;
+       pkt->ip_hdr.dadr = ans->pkt.to;
+
+       pkt->ip_hdr.chks = calculate_ip_checksum((uint16_t*)&pkt->ip_hdr, 5*4);
+
+       pkt->udp_dns.udp_hdr.spt = htons(53);
+       pkt->udp_dns.udp_hdr.dpt = ans->pkt.dst_port;
+       pkt->udp_dns.udp_hdr.len = htons(net_len - sizeof(struct ip_hdr));
+       pkt->udp_dns.udp_hdr.crc = 0; /* Optional for IPv4 */
+
+       memcpy(&pkt->udp_dns.data, ans->pkt.data, data_len);
+
+       /* GNUNET_MessageHeader
+        * pkt_tun
+        * ip_hdr
+        * udp_dns
+        *     udp_pkt
+             !!data!!
+        */
+       
+       GNUNET_CONTAINER_DLL_remove (mycls.answer_head, mycls.answer_tail, ans);
+       GNUNET_free(ans);
+
+       /* FIXME */ GNUNET_DISK_file_write(mycls.fh_to_helper, pkt, pkt_len);
+
+       /* TODO: if still in dll, reschedule */
 }
 
 size_t send_query(void* cls, size_t size, void* buf)