tproxy: added tproxy sockopt interface in the IPV6 layer

Support for IPV6_RECVORIGDSTADDR sockopt for UDP sockets were contributed by
Harry Mason.
Signed-off-by: Balazs Scheidler <bazsi@balabit.hu>
Signed-off-by: KOVACS Krisztian <hidden@balabit.hu>
Signed-off-by: Patrick McHardy <kaber@trash.net>

include/linux/in6.h

@@ -268,6 +268,10 @@ struct in6_flowlabel_req {
 /* RFC5082: Generalized Ttl Security Mechanism */
 #define IPV6_MINHOPCOUNT		73
 
+#define IPV6_ORIGDSTADDR        74
+#define IPV6_RECVORIGDSTADDR    IPV6_ORIGDSTADDR
+#define IPV6_TRANSPARENT        75
+
 /*
  * Multicast Routing:
  * see include/linux/mroute6.h.

include/linux/ipv6.h

@@ -341,7 +341,9 @@ struct ipv6_pinfo {
 				odstopts:1,
                                 rxflow:1,
 				rxtclass:1,
-				rxpmtu:1;
+				rxpmtu:1,
+				rxorigdstaddr:1;
+				/* 2 bits hole */
 		} bits;
 		__u16		all;
 	} rxopt;

net/ipv6/datagram.c

@@ -577,6 +577,25 @@ int datagram_recv_ctl(struct sock *sk, struct msghdr *msg, struct sk_buff *skb)
 		u8 *ptr = nh + opt->dst1;
 		put_cmsg(msg, SOL_IPV6, IPV6_2292DSTOPTS, (ptr[1]+1)<<3, ptr);
 	}
+	if (np->rxopt.bits.rxorigdstaddr) {
+		struct sockaddr_in6 sin6;
+		u16 *ports = (u16 *) skb_transport_header(skb);
+
+		if (skb_transport_offset(skb) + 4 <= skb->len) {
+			/* All current transport protocols have the port numbers in the
+			 * first four bytes of the transport header and this function is
+			 * written with this assumption in mind.
+			 */
+
+			sin6.sin6_family = AF_INET6;
+			ipv6_addr_copy(&sin6.sin6_addr, &ipv6_hdr(skb)->daddr);
+			sin6.sin6_port = ports[1];
+			sin6.sin6_flowinfo = 0;
+			sin6.sin6_scope_id = 0;
+
+			put_cmsg(msg, SOL_IPV6, IPV6_ORIGDSTADDR, sizeof(sin6), &sin6);
+		}
+	}
 	return 0;
 }
 

net/ipv6/ipv6_sockglue.c

@@ -342,6 +342,21 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		retv = 0;
 		break;
 
+	case IPV6_TRANSPARENT:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		/* we don't have a separate transparent bit for IPV6 we use the one in the IPv4 socket */
+		inet_sk(sk)->transparent = valbool;
+		retv = 0;
+		break;
+
+	case IPV6_RECVORIGDSTADDR:
+		if (optlen < sizeof(int))
+			goto e_inval;
+		np->rxopt.bits.rxorigdstaddr = valbool;
+		retv = 0;
+		break;
+
 	case IPV6_HOPOPTS:
 	case IPV6_RTHDRDSTOPTS:
 	case IPV6_RTHDR:
@@ -1104,6 +1119,14 @@ static int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		break;
 	}
 
+	case IPV6_TRANSPARENT:
+		val = inet_sk(sk)->transparent;
+		break;
+
+	case IPV6_RECVORIGDSTADDR:
+		val = np->rxopt.bits.rxorigdstaddr;
+		break;
+
 	case IPV6_UNICAST_HOPS:
 	case IPV6_MULTICAST_HOPS:
 	{