Go -> C++

backend/nfqueue/main.go

@@ -132,6 +132,8 @@ func handle_packets(packets <-chan netfilter.NFPacket, filter_table_channel chan
 			}
 		case p := <-packets:
 			{
+				p.SetVerdict(netfilter.NF_ACCEPT)
+				break
 				transport_layer := p.Packet.TransportLayer()
 				data := transport_layer.LayerPayload()
 				if len(data) > 0 {

backend/nfqueue/nfqueue.cpp

@@ -0,0 +1,204 @@
+#include <arpa/inet.h>
+#include <libmnl/libmnl.h>
+#include <type_traits>
+#include <tins/tins.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nfnetlink.h>
+#include <linux/types.h>
+#include <linux/netfilter/nfnetlink_queue.h>
+#include <libnetfilter_queue/libnetfilter_queue.h>
+#include <linux/netfilter/nfnetlink_conntrack.h>
+#include <stdexcept>
+#include <iostream>
+#include <cstring>
+#include <cstdlib>
+#include <cerrno>
+
+using namespace std;
+using namespace Tins;
+
+typedef bool NetFilterQueueCallback(const uint8_t*,uint32_t);
+typedef struct mnl_socket* NetFilterQueueSocket;
+
+PDU * find_transport_layer(PDU* pkt){
+	while(pkt != NULL){
+		if (pkt->pdu_type() == PDU::TCP || pkt->pdu_type() == PDU::UDP) {
+			return pkt;
+		}
+		pkt = pkt->inner_pdu();
+	}
+	return pkt;
+}
+
+template <NetFilterQueueCallback callback_func>
+class NetfilterQueue {
+	public:
+	size_t BUF_SIZE = 0xffff + (MNL_SOCKET_BUFFER_SIZE/2);
+	char *buf = NULL;
+	unsigned int portid;
+	u_int16_t queue_num;
+	NetFilterQueueSocket nl = NULL;
+
+	NetfilterQueue(u_int16_t queue_num): queue_num(queue_num) {
+		
+		struct nlmsghdr *nlh;
+		nl = mnl_socket_open(NETLINK_NETFILTER);
+		
+		if (nl == NULL) {
+			throw std::runtime_error( "mnl_socket_open" );
+		}
+
+		if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+			throw std::runtime_error( "mnl_socket_bind" );
+		}
+		portid = mnl_socket_get_portid(nl);
+
+		buf = (char*) malloc(BUF_SIZE);
+		if (!buf) {
+			throw std::runtime_error( "allocate receive buffer" );
+		}
+
+		nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
+		nfq_nlmsg_cfg_put_cmd(nlh, AF_INET, NFQNL_CFG_CMD_BIND);
+
+		if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
+			free(buf);
+			throw std::runtime_error( "mnl_socket_send" );
+		}
+
+		nlh = nfq_nlmsg_put(buf, NFQNL_MSG_CONFIG, queue_num);
+		nfq_nlmsg_cfg_put_params(nlh, NFQNL_COPY_PACKET, 0xffff);
+
+		mnl_attr_put_u32(nlh, NFQA_CFG_FLAGS, htonl(NFQA_CFG_F_GSO));
+		mnl_attr_put_u32(nlh, NFQA_CFG_MASK, htonl(NFQA_CFG_F_GSO));
+
+		if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
+			free(buf);
+			throw std::runtime_error( "mnl_socket_send" );
+		}
+
+	}
+
+	void run(){
+		/*
+		* ENOBUFS is signalled to userspace when packets were lost
+		* on kernel side.  In most cases, userspace isn't interested
+		* in this information, so turn it off.
+		*/
+		int ret = 1;
+		mnl_socket_setsockopt(nl, NETLINK_NO_ENOBUFS, &ret, sizeof(int));
+
+		for (;;) {
+			ret = mnl_socket_recvfrom(nl, buf, BUF_SIZE);
+			if (ret == -1) {
+				throw std::runtime_error( "mnl_socket_recvfrom" );
+			}
+
+			ret = mnl_cb_run(buf, ret, 0, portid, queue_cb, nl);
+			if (ret < 0){
+				throw std::runtime_error( "mnl_cb_run" );
+			}
+		}
+	}
+	
+	~NetfilterQueue() {
+		if (buf != NULL) {
+			free(buf);
+			buf = NULL;
+		}
+		mnl_socket_close(nl);
+	}
+	private:
+
+	static int queue_cb(const struct nlmsghdr *nlh, void *data)
+	{
+		NetFilterQueueSocket nl = (NetFilterQueueSocket)data;
+		//Extract attributes from the nlmsghdr
+		struct nlattr *attr[NFQA_MAX+1] = {};
+		
+		if (nfq_nlmsg_parse(nlh, attr) < 0) {
+			perror("problems parsing");
+			return MNL_CB_ERROR;
+		}
+		if (attr[NFQA_PACKET_HDR] == NULL) {
+			fputs("metaheader not set\n", stderr);
+			return MNL_CB_ERROR;
+		}	
+		//Get Payload
+		uint16_t plen = mnl_attr_get_payload_len(attr[NFQA_PAYLOAD]);
+		void *payload = mnl_attr_get_payload(attr[NFQA_PAYLOAD]);
+
+
+		//Return result to the kernel
+		struct nfqnl_msg_packet_hdr *ph = (nfqnl_msg_packet_hdr*) mnl_attr_get_payload(attr[NFQA_PACKET_HDR]);
+		struct nfgenmsg *nfg = (nfgenmsg *)mnl_nlmsg_get_payload(nlh);
+		char buf[MNL_SOCKET_BUFFER_SIZE];
+		struct nlmsghdr *nlh_verdict;
+		struct nlattr *nest;
+
+		nlh_verdict = nfq_nlmsg_put(buf, NFQNL_MSG_VERDICT, ntohs(nfg->res_id));
+
+		#define PKT_OPS \
+		PDU *transport_layer = find_transport_layer(&packet); \
+		if(transport_layer->inner_pdu() == nullptr){ \
+			nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT );\
+		}else{\
+			int size = transport_layer->inner_pdu()->size();\
+			if(callback_func((const uint8_t*)payload+plen - size, size)){\
+				nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT );\
+			} else{\
+				if (transport_layer->pdu_type() == PDU::TCP){\
+					((TCP *)transport_layer)->release_inner_pdu();\
+					((TCP *)transport_layer)->set_flag(TCP::FIN,1);\
+					((TCP *)transport_layer)->set_flag(TCP::ACK,1);\
+					((TCP *)transport_layer)->set_flag(TCP::SYN,0);\
+					nfq_nlmsg_verdict_put_pkt(nlh_verdict, packet.serialize().data(), packet.size());\
+					nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_ACCEPT );		\
+				}else{\
+					nfq_nlmsg_verdict_put(nlh_verdict, ntohl(ph->packet_id), NF_DROP );\
+				}\
+			}\
+		}\
+
+		if ( (((uint8_t*)payload)[0] & 0xf0) == 0x40 ){
+			IP packet = IP((uint8_t*)payload,plen);
+			PKT_OPS
+		}else{
+			IPv6 packet = IPv6((uint8_t*)payload,plen);
+			PKT_OPS
+		}	
+
+		/* example to set the connmark. First, start NFQA_CT section: */
+		nest = mnl_attr_nest_start(nlh_verdict, NFQA_CT);
+
+		/* then, add the connmark attribute: */
+		mnl_attr_put_u32(nlh_verdict, CTA_MARK, htonl(42));
+		/* more conntrack attributes, e.g. CTA_LABELS could be set here */
+
+		/* end conntrack section */
+		mnl_attr_nest_end(nlh_verdict, nest);
+
+		if (mnl_socket_sendto(nl, nlh_verdict, nlh_verdict->nlmsg_len) < 0) {
+			throw std::runtime_error( "mnl_socket_send" );
+		}
+
+		return MNL_CB_OK;
+	}
+
+};
+
+
+bool callb(const uint8_t *data, uint32_t len){
+	return true;
+}
+
+int main(int argc, char *argv[])
+{
+	if (argc != 2) {
+		printf("Usage: %s [queue_num]\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+	NetfilterQueue<callb>* queue = new NetfilterQueue<callb>(atoi(argv[1]));
+	queue->run();
+	return 0;
+}