src: add mangle functions for IPv6, IPv6/TCP and IPv6/UDP

Signed-off-by: Duncan Roe <duncan_roe@optusnet.com.au>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 108 insertions, 0 deletions

diff --git a/src/extra/ipv6.c b/src/extra/ipv6.c
index f685b3b..6e8820c 100644
--- a/src/extra/ipv6.c
+++ b/src/extra/ipv6.c
@@ -117,6 +117,35 @@ int nfq_ip6_set_transport_header(struct pkt_buff *pktb, struct ip6_hdr *ip6h,
 }
 
 /**
+ * nfq_ip6_mangle - mangle IPv6 packet buffer
+ * \param pktb: Pointer to user-space network packet buffer
+ * \param dataoff: Offset to layer 4 header
+ * \param match_offset: Offset to content that you want to mangle
+ * \param match_len: Length of the existing content you want to mangle
+ * \param rep_buffer: Pointer to data you want to use to replace current content
+ * \param rep_len: Length of data you want to use to replace current content
+ * \returns 1 for success and 0 for failure. See pktb_mangle() for failure case
+ * \note This function updates the IPv6 length (if necessary)
+ */
+EXPORT_SYMBOL
+int nfq_ip6_mangle(struct pkt_buff *pktb, unsigned int dataoff,
+		   unsigned int match_offset, unsigned int match_len,
+		   const char *rep_buffer, unsigned int rep_len)
+{
+	struct ip6_hdr *ip6h = (struct ip6_hdr *)pktb->network_header;
+
+	if (!pktb_mangle(pktb, dataoff, match_offset, match_len, rep_buffer,
+			 rep_len))
+		return 0;
+
+	/* Fix IPv6 hdr length information */
+	ip6h->ip6_plen =
+		htons(pktb->tail - pktb->network_header - sizeof *ip6h);
+
+	return 1;
+}
+
+/**
  * nfq_ip6_snprintf - print IPv6 header into one buffer in iptables LOG format
  * \param buf: Pointer to buffer that is used to print the object
  * \param size: Size of the buffer (or remaining room in it).
diff --git a/src/extra/tcp.c b/src/extra/tcp.c
index 136d7ea..8119843 100644
--- a/src/extra/tcp.c
+++ b/src/extra/tcp.c
@@ -21,6 +21,7 @@
 #include <libnetfilter_queue/libnetfilter_queue.h>
 #include <libnetfilter_queue/libnetfilter_queue_tcp.h>
 #include <libnetfilter_queue/libnetfilter_queue_ipv4.h>
+#include <libnetfilter_queue/libnetfilter_queue_ipv6.h>
 #include <libnetfilter_queue/pktbuff.h>
 
 #include "internal.h"
@@ -207,5 +208,44 @@ int nfq_tcp_mangle_ipv4(struct pkt_buff *pkt,
 }
 
 /**
+ * nfq_tcp_mangle_ipv6 - Mangle TCP/IPv6 packet buffer
+ * \param pktb: Pointer to network packet buffer
+ * \param match_offset: Offset from start of TCP data of content that you want
+ * to mangle
+ * \param match_len: Length of the existing content you want to mangle
+ * \param rep_buffer: Pointer to data you want to use to replace current content
+ * \param rep_len: Length of data you want to use to replace current content
+ * \returns 1 for success and 0 for failure. See pktb_mangle() for failure case
+ * \note This function updates the IPv6 length and recalculates the TCP
+ * checksum for you.
+ * \warning After changing the length of a TCP message, the application will
+ * need to mangle sequence numbers in both directions until another change
+ * puts them in sync again
+ */
+EXPORT_SYMBOL
+int nfq_tcp_mangle_ipv6(struct pkt_buff *pktb,
+			unsigned int match_offset, unsigned int match_len,
+			const char *rep_buffer, unsigned int rep_len)
+{
+	struct ip6_hdr *ip6h;
+	struct tcphdr *tcph;
+
+	ip6h = (struct ip6_hdr *)pktb->network_header;
+	tcph = (struct tcphdr *)(pktb->transport_header);
+	if (!tcph)
+		return 0;
+
+	if (!nfq_ip6_mangle(pktb,
+			   pktb->transport_header - pktb->network_header +
+			   tcph->doff * 4,
+			   match_offset, match_len, rep_buffer, rep_len))
+		return 0;
+
+	nfq_tcp_compute_checksum_ipv6(tcph, ip6h);
+
+	return 1;
+}
+
+/**
  * @}
  */
diff --git a/src/extra/udp.c b/src/extra/udp.c
index 34dbf2a..9eee1c7 100644
--- a/src/extra/udp.c
+++ b/src/extra/udp.c
@@ -20,6 +20,7 @@
 #include <libnetfilter_queue/libnetfilter_queue.h>
 #include <libnetfilter_queue/libnetfilter_queue_udp.h>
 #include <libnetfilter_queue/libnetfilter_queue_ipv4.h>
+#include <libnetfilter_queue/libnetfilter_queue_ipv6.h>
 #include <libnetfilter_queue/pktbuff.h>
 
 #include "internal.h"
@@ -160,6 +161,44 @@ int nfq_udp_mangle_ipv4(struct pkt_buff *pktb,
 }
 
 /**
+ * nfq_udp_mangle_ipv6 - Mangle UDP/IPv6 packet buffer
+ * \param pktb: Pointer to network packet buffer
+ * \param match_offset: Offset from start of UDP data of content that you want
+ * to mangle
+ * \param match_len: Length of the existing content you want to mangle
+ * \param rep_buffer: Pointer to data you want to use to replace current content
+ * \param rep_len: Length of data you want to use to replace current content
+ * \returns 1 for success and 0 for failure. See pktb_mangle() for failure case
+ * \note This function updates the IPv6 and UDP lengths and recalculates the UDP
+ * checksum for you.
+ */
+EXPORT_SYMBOL
+int nfq_udp_mangle_ipv6(struct pkt_buff *pktb,
+			unsigned int match_offset, unsigned int match_len,
+			const char *rep_buffer, unsigned int rep_len)
+{
+	struct ip6_hdr *ip6h;
+	struct udphdr *udph;
+
+	ip6h = (struct ip6_hdr *)pktb->network_header;
+	udph = (struct udphdr *)(pktb->transport_header);
+	if (!udph)
+		return 0;
+
+	udph->len = htons(ntohs(udph->len) + rep_len - match_len);
+
+	if (!nfq_ip6_mangle(pktb,
+			    pktb->transport_header - pktb->network_header +
+			    sizeof(struct udphdr),
+			    match_offset, match_len, rep_buffer, rep_len))
+		return 0;
+
+	nfq_udp_compute_checksum_ipv6(udph, ip6h);
+
+	return 1;
+}
+
+/**
  * nfq_pkt_snprintf_udp_hdr - print udp header into one buffer in a humnan
  * readable way
  * \param buf: pointer to buffer that is used to print the object