[PATCH 0/2] IPv4-mapped on wire, :: dst address issue

[PATCH 0/2] IPv4-mapped on wire, :: dst address issue

[Jonathan T. Leighton]

Under some circumstances IPv6 datagrams are sent with IPv4-mapped IPv6
addresses as the source. Given an IPv6 socket bound to an IPv4-mapped
IPv6 address, and an IPv6 destination address, both TCP and UDP will
will send packets using the IPv4-mapped IPv6 address as the source. Per
RFC 6890 (Table 20), IPv4-mapped IPv6 source addresses are not allowed
in an IP datagram. The problem can be observed by attempting to
connect() either a TCP or UDP socket, or by using sendmsg() with a UDP
socket. The patch is intended to correct this issue for all socket
types.

linux follows the BSD convention that an IPv6 destination address
specified as in6addr_any is converted to the loopback address.
Currently, neither TCP nor UDP consider the possibility that the source
address is an IPv4-mapped IPv6 address, and assume that the appropriate
loopback address is ::1. The patch adds a check on whether or not the
source address is an IPv4-mapped IPv6 address and then sets the
destination address to either ::ffff:127.0.0.1 or ::1, as appropriate.

Jon

Jonathan T. Leighton (2):
  ipv6: Inhibit IPv4-mapped src address on the wire.
  ipv6: Handle IPv4-mapped src to in6addr_any dst.

 net/ipv6/datagram.c   | 14 +++++++++-----
 net/ipv6/ip6_output.c |  3 +++
 net/ipv6/tcp_ipv6.c   | 11 ++++++++---
 net/ipv6/udp.c        |  4 ++++
 4 files changed, 24 insertions(+), 8 deletions(-)

-- 
2.7.4

[PATCH 1/2] ipv6: Inhibit IPv4-mapped src address on the wire.

[Jonathan T. Leighton]

This patch adds a check for the problematic case of an IPv4-mapped IPv6
source address and a destination address that is neither an IPv4-mapped
IPv6 address nor in6addr_any, and returns an appropriate error. The
check in done before returning from looking up the route.

Signed-off-by: Jonathan T. Leighton <jtleight@udel.edu>
---
 net/ipv6/ip6_output.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index a75871c..d0f51b4 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1022,6 +1022,9 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk,
 		}
 	}
 #endif
+	if (ipv6_addr_v4mapped(&fl6->saddr) &&
+	    !(ipv6_addr_v4mapped(&fl6->daddr) || ipv6_addr_any(&fl6->daddr)))
+		return -EAFNOSUPPORT;
 
 	return 0;
 
-- 
2.7.4

[PATCH 2/2] ipv6: Handle IPv4-mapped src to in6addr_any dst.

[Jonathan T. Leighton]

This patch adds a check on the type of the source address for the case
where the destination address is in6addr_any. If the source is an
IPv4-mapped IPv6 source address, the destination is changed to
::ffff:127.0.0.1, and otherwise the destination is changed to ::1. This
is done in three locations to handle UDP calls to either connect() or
sendmsg() and TCP calls to connect(). Note that udpv6_sendmsg() delays
handling an in6addr_any destination until very late, so the patch only
needs to handle the case where the source is an IPv4-mapped IPv6
address.

Signed-off-by: Jonathan T. Leighton <jtleight@udel.edu>
---
 net/ipv6/datagram.c | 14 +++++++++-----
 net/ipv6/tcp_ipv6.c | 11 ++++++++---
 net/ipv6/udp.c      |  4 ++++
 3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index a3eaafd..eec27f8 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -167,18 +167,22 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
 	if (np->sndflow)
 		fl6_flowlabel = usin->sin6_flowinfo & IPV6_FLOWINFO_MASK;
 
-	addr_type = ipv6_addr_type(&usin->sin6_addr);
-
-	if (addr_type == IPV6_ADDR_ANY) {
+	if (ipv6_addr_any(&usin->sin6_addr)) {
 		/*
 		 *	connect to self
 		 */
-		usin->sin6_addr.s6_addr[15] = 0x01;
+		if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
+			ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK),
+					       &usin->sin6_addr);
+		else
+			usin->sin6_addr = in6addr_loopback;
 	}
 
+	addr_type = ipv6_addr_type(&usin->sin6_addr);
+
 	daddr = &usin->sin6_addr;
 
-	if (addr_type == IPV6_ADDR_MAPPED) {
+	if (addr_type & IPV6_ADDR_MAPPED) {
 		struct sockaddr_in sin;
 
 		if (__ipv6_only_sock(sk)) {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index b5d2721..21c7199 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -149,8 +149,13 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	 *	connect() to INADDR_ANY means loopback (BSD'ism).
 	 */
 
-	if (ipv6_addr_any(&usin->sin6_addr))
-		usin->sin6_addr.s6_addr[15] = 0x1;
+	if (ipv6_addr_any(&usin->sin6_addr)) {
+		if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr))
+			ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK),
+					       &usin->sin6_addr);
+		else
+			usin->sin6_addr = in6addr_loopback;
+	}
 
 	addr_type = ipv6_addr_type(&usin->sin6_addr);
 
@@ -189,7 +194,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	 *	TCP over IPv4
 	 */
 
-	if (addr_type == IPV6_ADDR_MAPPED) {
+	if (addr_type & IPV6_ADDR_MAPPED) {
 		u32 exthdrlen = icsk->icsk_ext_hdr_len;
 		struct sockaddr_in sin;
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index df71ba0..4e4c401 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1046,6 +1046,10 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 			if (addr_len < SIN6_LEN_RFC2133)
 				return -EINVAL;
 			daddr = &sin6->sin6_addr;
+			if (ipv6_addr_any(daddr) &&
+			    ipv6_addr_v4mapped(&np->saddr))
+				ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK),
+						       daddr);
 			break;
 		case AF_INET:
 			goto do_udp_sendmsg;
-- 
2.7.4

Re: [PATCH 0/2] IPv4-mapped on wire, :: dst address issue

[David Miller]

From: "Jonathan T. Leighton" <jtleight@udel.edu>
Date: Sun, 12 Feb 2017 17:26:05 -0500

> Under some circumstances IPv6 datagrams are sent with IPv4-mapped IPv6
> addresses as the source. Given an IPv6 socket bound to an IPv4-mapped
> IPv6 address, and an IPv6 destination address, both TCP and UDP will
> will send packets using the IPv4-mapped IPv6 address as the source. Per
> RFC 6890 (Table 20), IPv4-mapped IPv6 source addresses are not allowed
> in an IP datagram. The problem can be observed by attempting to
> connect() either a TCP or UDP socket, or by using sendmsg() with a UDP
> socket. The patch is intended to correct this issue for all socket
> types.
> 
> linux follows the BSD convention that an IPv6 destination address
> specified as in6addr_any is converted to the loopback address.
> Currently, neither TCP nor UDP consider the possibility that the source
> address is an IPv4-mapped IPv6 address, and assume that the appropriate
> loopback address is ::1. The patch adds a check on whether or not the
> source address is an IPv4-mapped IPv6 address and then sets the
> destination address to either ::ffff:127.0.0.1 or ::1, as appropriate.

Series applied, thanks.