[PATCH v2 2/4] tcp: md5: Allow MD5SIG_FLAG_IFINDEX with ifindex=0

[Leonard Crestez <cdleonard@gmail.com>]

Multiple VRFs are generally meant to be "separate" but right now md5
keys for the default VRF also affect connections inside VRFs if the IP
addresses happen to overlap.

So far the combination of TCP_MD5SIG_IFINDEX with tcpm_ifindex == 0
was an error, accept this to mean "key only applies to default VRF".
This is what applications using VRFs for traffic separation want.

Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
---
 include/net/tcp.h   |  5 +++--
 net/ipv4/tcp_ipv4.c | 26 ++++++++++++++++----------
 net/ipv6/tcp_ipv6.c | 15 +++++++++------
 3 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4c2898ac6569..10f3a37eceb2 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1588,10 +1588,11 @@ union tcp_md5_addr {
 struct tcp_md5sig_key {
 	struct hlist_node	node;
 	u8			keylen;
 	u8			family; /* AF_INET or AF_INET6 */
 	u8			prefixlen;
+	u8			flags;
 	union tcp_md5_addr	addr;
 	int			l3index; /* set if key added with L3 scope */
 	u8			key[TCP_MD5SIG_MAXKEYLEN];
 	struct rcu_head		rcu;
 };
@@ -1633,14 +1634,14 @@ struct tcp_md5sig_pool {
 
 /* - functions */
 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
 			const struct sock *sk, const struct sk_buff *skb);
 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
-		   int family, u8 prefixlen, int l3index,
+		   int family, u8 prefixlen, int l3index, u8 flags,
 		   const u8 *newkey, u8 newkeylen, gfp_t gfp);
 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
-		   int family, u8 prefixlen, int l3index);
+		   int family, u8 prefixlen, int l3index, u8 flags);
 struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 					 const struct sock *addr_sk);
 
 #ifdef CONFIG_TCP_MD5SIG
 #include <linux/jump_label.h>
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a9a6a6d598c6..5e6d8cb82ce5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1071,11 +1071,11 @@ struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
 
 	hlist_for_each_entry_rcu(key, &md5sig->head, node,
 				 lockdep_sock_is_held(sk)) {
 		if (key->family != family)
 			continue;
-		if (key->l3index && key->l3index != l3index)
+		if (key->flags & TCP_MD5SIG_FLAG_IFINDEX && key->l3index != l3index)
 			continue;
 		if (family == AF_INET) {
 			mask = inet_make_mask(key->prefixlen);
 			match = (key->addr.a4.s_addr & mask) ==
 				(addr->a4.s_addr & mask);
@@ -1096,11 +1096,11 @@ struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
 EXPORT_SYMBOL(__tcp_md5_do_lookup);
 
 static struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
 						      const union tcp_md5_addr *addr,
 						      int family, u8 prefixlen,
-						      int l3index)
+						      int l3index, u8 flags)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_key *key;
 	unsigned int size = sizeof(struct in_addr);
 	const struct tcp_md5sig_info *md5sig;
@@ -1116,10 +1116,12 @@ static struct tcp_md5sig_key *tcp_md5_do_lookup_exact(const struct sock *sk,
 #endif
 	hlist_for_each_entry_rcu(key, &md5sig->head, node,
 				 lockdep_sock_is_held(sk)) {
 		if (key->family != family)
 			continue;
+		if ((key->flags & TCP_MD5SIG_FLAG_IFINDEX) != (flags & TCP_MD5SIG_FLAG_IFINDEX))
+			continue;
 		if (key->l3index != l3index)
 			continue;
 		if (!memcmp(&key->addr, addr, size) &&
 		    key->prefixlen == prefixlen)
 			return key;
@@ -1140,19 +1142,19 @@ struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
 }
 EXPORT_SYMBOL(tcp_v4_md5_lookup);
 
 /* This can be called on a newly created socket, from other files */
 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
-		   int family, u8 prefixlen, int l3index,
+		   int family, u8 prefixlen, int l3index, u8 flags,
 		   const u8 *newkey, u8 newkeylen, gfp_t gfp)
 {
 	/* Add Key to the list */
 	struct tcp_md5sig_key *key;
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct tcp_md5sig_info *md5sig;
 
-	key = tcp_md5_do_lookup_exact(sk, addr, family, prefixlen, l3index);
+	key = tcp_md5_do_lookup_exact(sk, addr, family, prefixlen, l3index, flags);
 	if (key) {
 		/* Pre-existing entry - just update that one.
 		 * Note that the key might be used concurrently.
 		 * data_race() is telling kcsan that we do not care of
 		 * key mismatches, since changing MD5 key on live flows
@@ -1193,24 +1195,25 @@ int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
 	memcpy(key->key, newkey, newkeylen);
 	key->keylen = newkeylen;
 	key->family = family;
 	key->prefixlen = prefixlen;
 	key->l3index = l3index;
+	key->flags = flags;
 	memcpy(&key->addr, addr,
 	       (family == AF_INET6) ? sizeof(struct in6_addr) :
 				      sizeof(struct in_addr));
 	hlist_add_head_rcu(&key->node, &md5sig->head);
 	return 0;
 }
 EXPORT_SYMBOL(tcp_md5_do_add);
 
 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family,
-		   u8 prefixlen, int l3index)
+		   u8 prefixlen, int l3index, u8 flags)
 {
 	struct tcp_md5sig_key *key;
 
-	key = tcp_md5_do_lookup_exact(sk, addr, family, prefixlen, l3index);
+	key = tcp_md5_do_lookup_exact(sk, addr, family, prefixlen, l3index, flags);
 	if (!key)
 		return -ENOENT;
 	hlist_del_rcu(&key->node);
 	atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
 	kfree_rcu(key, rcu);
@@ -1240,28 +1243,31 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
 	struct tcp_md5sig cmd;
 	struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.tcpm_addr;
 	const union tcp_md5_addr *addr;
 	u8 prefixlen = 32;
 	int l3index = 0;
+	u8 flags;
 
 	if (optlen < sizeof(cmd))
 		return -EINVAL;
 
 	if (copy_from_sockptr(&cmd, optval, sizeof(cmd)))
 		return -EFAULT;
 
 	if (sin->sin_family != AF_INET)
 		return -EINVAL;
 
+	flags = cmd.tcpm_flags & TCP_MD5SIG_FLAG_IFINDEX;
+
 	if (optname == TCP_MD5SIG_EXT &&
 	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_PREFIX) {
 		prefixlen = cmd.tcpm_prefixlen;
 		if (prefixlen > 32)
 			return -EINVAL;
 	}
 
-	if (optname == TCP_MD5SIG_EXT &&
+	if (optname == TCP_MD5SIG_EXT && cmd.tcpm_ifindex &&
 	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_IFINDEX) {
 		struct net_device *dev;
 
 		rcu_read_lock();
 		dev = dev_get_by_index_rcu(sock_net(sk), cmd.tcpm_ifindex);
@@ -1278,16 +1284,16 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
 	}
 
 	addr = (union tcp_md5_addr *)&sin->sin_addr.s_addr;
 
 	if (!cmd.tcpm_keylen)
-		return tcp_md5_do_del(sk, addr, AF_INET, prefixlen, l3index);
+		return tcp_md5_do_del(sk, addr, AF_INET, prefixlen, l3index, flags);
 
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
 
-	return tcp_md5_do_add(sk, addr, AF_INET, prefixlen, l3index,
+	return tcp_md5_do_add(sk, addr, AF_INET, prefixlen, l3index, flags,
 			      cmd.tcpm_key, cmd.tcpm_keylen, GFP_KERNEL);
 }
 
 static int tcp_v4_md5_hash_headers(struct tcp_md5sig_pool *hp,
 				   __be32 daddr, __be32 saddr,
@@ -1607,11 +1613,11 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
 		 * We're using one, so create a matching key
 		 * on the newsk structure. If we fail to get
 		 * memory, then we end up not copying the key
 		 * across. Shucks.
 		 */
-		tcp_md5_do_add(newsk, addr, AF_INET, 32, l3index,
+		tcp_md5_do_add(newsk, addr, AF_INET, 32, l3index, key->flags,
 			       key->key, key->keylen, GFP_ATOMIC);
 		sk_nocaps_add(newsk, NETIF_F_GSO_MASK);
 	}
 #endif
 
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 8cf5ff2e9504..1ef27cd7dbff 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -597,31 +597,34 @@ static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
 {
 	struct tcp_md5sig cmd;
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd.tcpm_addr;
 	int l3index = 0;
 	u8 prefixlen;
+	u8 flags;
 
 	if (optlen < sizeof(cmd))
 		return -EINVAL;
 
 	if (copy_from_sockptr(&cmd, optval, sizeof(cmd)))
 		return -EFAULT;
 
 	if (sin6->sin6_family != AF_INET6)
 		return -EINVAL;
 
+	flags = cmd.tcpm_flags & TCP_MD5SIG_FLAG_IFINDEX;
+
 	if (optname == TCP_MD5SIG_EXT &&
 	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_PREFIX) {
 		prefixlen = cmd.tcpm_prefixlen;
 		if (prefixlen > 128 || (ipv6_addr_v4mapped(&sin6->sin6_addr) &&
 					prefixlen > 32))
 			return -EINVAL;
 	} else {
 		prefixlen = ipv6_addr_v4mapped(&sin6->sin6_addr) ? 32 : 128;
 	}
 
-	if (optname == TCP_MD5SIG_EXT &&
+	if (optname == TCP_MD5SIG_EXT && cmd.tcpm_ifindex &&
 	    cmd.tcpm_flags & TCP_MD5SIG_FLAG_IFINDEX) {
 		struct net_device *dev;
 
 		rcu_read_lock();
 		dev = dev_get_by_index_rcu(sock_net(sk), cmd.tcpm_ifindex);
@@ -638,26 +641,26 @@ static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
 
 	if (!cmd.tcpm_keylen) {
 		if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 			return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
 					      AF_INET, prefixlen,
-					      l3index);
+					      l3index, flags);
 		return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
-				      AF_INET6, prefixlen, l3index);
+				      AF_INET6, prefixlen, l3index, flags);
 	}
 
 	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
 		return -EINVAL;
 
 	if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 		return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
-				      AF_INET, prefixlen, l3index,
+				      AF_INET, prefixlen, l3index, flags,
 				      cmd.tcpm_key, cmd.tcpm_keylen,
 				      GFP_KERNEL);
 
 	return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
-			      AF_INET6, prefixlen, l3index,
+			      AF_INET6, prefixlen, l3index, flags,
 			      cmd.tcpm_key, cmd.tcpm_keylen, GFP_KERNEL);
 }
 
 static int tcp_v6_md5_hash_headers(struct tcp_md5sig_pool *hp,
 				   const struct in6_addr *daddr,
@@ -1402,11 +1405,11 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
 		 * on the newsk structure. If we fail to get
 		 * memory, then we end up not copying the key
 		 * across. Shucks.
 		 */
 		tcp_md5_do_add(newsk, (union tcp_md5_addr *)&newsk->sk_v6_daddr,
-			       AF_INET6, 128, l3index, key->key, key->keylen,
+			       AF_INET6, 128, l3index, key->flags, key->key, key->keylen,
 			       sk_gfp_mask(sk, GFP_ATOMIC));
 	}
 #endif
 
 	if (__inet_inherit_port(sk, newsk) < 0) {
-- 
2.25.1