add pkt_buff and protocol helper functions

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 175 insertions, 0 deletions

diff --git a/src/extra/tcp.c b/src/extra/tcp.c
new file mode 100644
index 0000000..9de3748
--- /dev/null
+++ b/src/extra/tcp.c
@@ -0,0 +1,175 @@
+/*
+ * (C) 2012 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * 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 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This code has been sponsored by Vyatta Inc. <http://www.vyatta.com>
+ */
+
+#include <stdio.h>
+#include <string.h> /* for memcpy */
+#include <arpa/inet.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/tcp.h>
+
+#include <libnetfilter_queue/libnetfilter_queue.h>
+#include <libnetfilter_queue/libnetfilter_queue_tcp.h>
+#include <libnetfilter_queue/pktbuff.h>
+
+#include "internal.h"
+
+/**
+ * \defgroup tcp TCP helper functions
+ * @{
+ */
+
+/**
+ * nfq_tcp_get - get the TCP header
+ * \param pktb: pointer to user-space network packet buffer
+ *
+ * This function returns NULL if an invalid TCP header is found. On success,
+ * it returns the TCP header.
+ *
+ * \note You have to call nfq_ip_set_transport_header or
+ * nfq_ip6_set_transport_header first to access the TCP header.
+ */
+struct tcphdr *nfq_tcp_get_hdr(struct pkt_buff *pktb)
+{
+	if (pktb->transport_header == NULL)
+		return NULL;
+
+	/* No room for the TCP header. */
+	if (pktb->tail - pktb->transport_header < sizeof(struct tcphdr))
+		return NULL;
+
+	return (struct tcphdr *)pktb->transport_header;
+}
+EXPORT_SYMBOL(nfq_tcp_get_hdr);
+
+/**
+ * nfq_tcp_get_payload - get the TCP packet payload
+ * \param tcph: pointer to the TCP header
+ * \param pktb: pointer to user-space network packet buffer
+ */
+void *nfq_tcp_get_payload(struct tcphdr *tcph, struct pkt_buff *pktb)
+{
+	unsigned int doff = tcph->doff * 4;
+
+	/* malformed TCP data offset. */
+	if (pktb->transport_header + doff >= pktb->tail)
+		return NULL;
+
+	return pktb->transport_header + doff;
+}
+EXPORT_SYMBOL(nfq_tcp_get_payload);
+
+/**
+ * nfq_tcp_get_payload_len - get the tcp packet payload
+ * \param tcph: pointer to the TCP header
+ * \param pktb: pointer to user-space network packet buffer
+ */
+unsigned int
+nfq_tcp_get_payload_len(struct tcphdr *tcph, struct pkt_buff *pktb)
+{
+	return pktb->tail - pktb->transport_header;
+}
+EXPORT_SYMBOL(nfq_tcp_get_payload_len);
+
+/**
+ * nfq_tcp_set_checksum_ipv4 - computes IPv4/TCP packet checksum
+ * \param tcph: pointer to the TCP header
+ * \param iph: pointer to the IPv4 header
+ */
+void
+nfq_tcp_compute_checksum_ipv4(struct tcphdr *tcph, struct iphdr *iph)
+{
+	/* checksum field in header needs to be zero for calculation. */
+	tcph->check = 0;
+	tcph->check = checksum_tcpudp_ipv4(iph);
+}
+EXPORT_SYMBOL(nfq_tcp_compute_checksum_ipv4);
+
+/**
+ * nfq_tcp_set_checksum_ipv6 - computes IPv6/TCP packet checksum
+ * \param tcph: pointer to the TCP header
+ * \param iph: pointer to the IPv6 header
+ */
+void
+nfq_tcp_compute_checksum_ipv6(struct tcphdr *tcph, struct ip6_hdr *ip6h)
+{
+	/* checksum field in header needs to be zero for calculation. */
+	tcph->check = 0;
+	tcph->check = checksum_tcpudp_ipv6(ip6h, tcph);
+}
+EXPORT_SYMBOL(nfq_tcp_compute_checksum_ipv6);
+
+/*
+ *	The union cast uses a gcc extension to avoid aliasing problems
+ *  (union is compatible to any of its members)
+ *  This means this part of the code is -fstrict-aliasing safe now.
+ */
+union tcp_word_hdr {
+	struct tcphdr hdr;
+	uint32_t  words[5];
+};
+
+#define tcp_flag_word(tp) ( ((union tcp_word_hdr *)(tp))->words[3])
+
+/**
+ * nfq_pkt_snprintf_tcp_hdr - print tcp header into one buffer in a humnan
+ * readable way
+ * \param buf: pointer to buffer that is used to print the object
+ * \param size: size of the buffer (or remaining room in it).
+ * \param tcp: pointer to a valid tcp header.
+ *
+ */
+int nfq_tcp_snprintf(char *buf, size_t size, const struct tcphdr *tcph)
+{
+	int ret, len = 0;
+
+#define TCP_RESERVED_BITS htonl(0x0F000000)
+
+	ret = snprintf(buf, size, "SPT=%u DPT=%u SEQ=%u ACK=%u "
+				   "WINDOW=%u RES=%0x%02x ",
+			ntohs(tcph->source), ntohs(tcph->dest),
+			ntohl(tcph->seq), ntohl(tcph->ack_seq),
+			ntohs(tcph->window),
+			(uint8_t)(ntohl(tcp_flag_word(tcph) &
+				TCP_RESERVED_BITS) >> 22));
+	len += ret;
+
+	if (tcph->urg) {
+		ret = snprintf(buf+len, size-len, "URG ");
+		len += ret;
+	}
+	if (tcph->ack) {
+		ret = snprintf(buf+len, size-len, "ACK ");
+		len += ret;
+	}
+	if (tcph->psh) {
+		ret = snprintf(buf+len, size-len, "PSH ");
+		len += ret;
+	}
+	if (tcph->rst) {
+		ret = snprintf(buf+len, size-len, "RST ");
+		len += ret;
+	}
+	if (tcph->syn) {
+		ret = snprintf(buf+len, size-len, "SYN ");
+		len += ret;
+	}
+	if (tcph->fin) {
+		ret = snprintf(buf+len, size-len, "FIN ");
+		len += ret;
+	}
+	/* Not TCP options implemented yet, sorry. */
+}
+EXPORT_SYMBOL(nfq_tcp_snprintf);
+
+/**
+ * @}
+ */