[PATCH v4 13/19] tcp: authopt: Add initial l3index support

23 Dec 2021

This is a parallel feature to tcp_md5sig.tcpm_ifindex support and allows
applications to server multiple VRFs with a single socket.
The ifindex argument must be the ifindex of a VRF device and must match
exactly, keys with ifindex == 0 (outside of VRF) will not match for
connections inside a VRF.
Keys without the TCP_AUTHOPT_KEY_IFINDEX will ignore ifindex and match
both inside and outside VRF.
Signed-off-by: Leonard Crestez cdleonard@gmail.com
---
 Documentation/networking/tcp_authopt.rst |  1 +
 include/net/tcp_authopt.h                |  2 +
 include/uapi/linux/tcp.h                 | 11 ++++
 net/ipv4/tcp_authopt.c                   | 71 ++++++++++++++++++++++--
 4 files changed, 80 insertions(+), 5 deletions(-)

diff --git a/Documentation/networking/tcp_authopt.rst b/Documentation/networking/tcp_authopt.rst
index f29fdea7769f..f681d2221ce3 100644
--- a/Documentation/networking/tcp_authopt.rst
+++ b/Documentation/networking/tcp_authopt.rst
@@ -37,10 +37,11 @@ expand over time by increasing the size of `struct tcp_authopt_key` and adding
 new flags.
* Address binding is optional, by default keys match all addresses
  * Local address is ignored, matching is done by remote address
  * Ports are ignored
+ * It is possible to match a specific VRF by l3index (default is to ignore)
RFC5925 requires that key ids do not overlap when tcp identifiers (addr/port)
 overlap. This is not enforced by linux, configuring ambiguous keys will result
 in packet drops and lost connections.
diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h
index 3d03fbb186ef..800fde277239 100644
--- a/include/net/tcp_authopt.h
+++ b/include/net/tcp_authopt.h
@@ -45,10 +45,12 @@ struct tcp_authopt_key_info {
    u8 alg_id;
    /** @keylen: Same as &tcp_authopt_key.keylen */
    u8 keylen;
    /** @key: Same as &tcp_authopt_key.key */
    u8 key[TCP_AUTHOPT_MAXKEYLEN];
+	/** @l3index: Same as &tcp_authopt_key.ifindex */
+	int l3index;
    /** @addr: Same as &tcp_authopt_key.addr */
    struct sockaddr_storage addr;
    /** @alg: Algorithm implementation matching alg_id */
    struct tcp_authopt_alg_imp *alg;
 };
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index e02176390519..a7f5f918ed5a 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -400,15 +400,17 @@ struct tcp_authopt {
  * enum tcp_authopt_key_flag - flags for `tcp_authopt.flags`
  *
  * @TCP_AUTHOPT_KEY_DEL: Delete the key and ignore non-id fields
  * @TCP_AUTHOPT_KEY_EXCLUDE_OPTS: Exclude TCP options from signature
  * @TCP_AUTHOPT_KEY_ADDR_BIND: Key only valid for `tcp_authopt.addr`
+ * @TCP_AUTHOPT_KEY_IFINDEX: Key only valid for `tcp_authopt.ifindex`
  */
 enum tcp_authopt_key_flag {
    TCP_AUTHOPT_KEY_DEL = (1 << 0),
    TCP_AUTHOPT_KEY_EXCLUDE_OPTS = (1 << 1),
    TCP_AUTHOPT_KEY_ADDR_BIND = (1 << 2),
+	TCP_AUTHOPT_KEY_IFINDEX = (1 << 3),
 };
/**
  * enum tcp_authopt_alg - Algorithms for TCP Authentication Option
  */
@@ -450,10 +452,19 @@ struct tcp_authopt_key {
     * @addr: Key is only valid for this address
     *
     * Ignored unless TCP_AUTHOPT_KEY_ADDR_BIND flag is set
     */
    struct __kernel_sockaddr_storage addr;
+	/**
+	 * @ifindex: ifindex of vrf (l3mdev_master) interface
+	 *
+	 * If the TCP_AUTHOPT_KEY_IFINDEX flag is set then key only applies for
+	 * connections through this interface. Interface must be an vrf master.
+	 *
+	 * This is similar to `tcp_msg5sig.tcpm_ifindex`
+	 */
+	int	ifindex;
 };
/* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */
#define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1
diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index f0d7a7facfb9..f3e244d036c3 100644
--- a/net/ipv4/tcp_authopt.c
+++ b/net/ipv4/tcp_authopt.c
@@ -1,8 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
#include <net/tcp_authopt.h>
+#include <net/ip.h>
 #include <net/ipv6.h>
 #include <net/tcp.h>
 #include <linux/kref.h>
 #include <crypto/hash.h>
@@ -261,10 +262,14 @@ static bool tcp_authopt_key_match_exact(struct tcp_authopt_key_info *info,
 {
    if (info->send_id != key->send_id)
    	return false;
    if (info->recv_id != key->recv_id)
    	return false;
+	if ((info->flags & TCP_AUTHOPT_KEY_IFINDEX) != (key->flags & TCP_AUTHOPT_KEY_IFINDEX))
+		return false;
+	if ((info->flags & TCP_AUTHOPT_KEY_IFINDEX) && info->l3index != key->ifindex)
+		return false;
    if ((info->flags & TCP_AUTHOPT_KEY_ADDR_BIND) != (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND))
    	return false;
    if (info->flags & TCP_AUTHOPT_KEY_ADDR_BIND)
    	if (!ipvx_addr_match(&info->addr, &key->addr))
    		return false;
@@ -328,26 +333,49 @@ static struct tcp_authopt_key_info *tcp_authopt_key_lookup_exact(const struct so
    		return key_info;
return NULL;
 }
+static bool better_key_match(struct tcp_authopt_key_info *old, struct tcp_authopt_key_info *new)
+{
+	if (!old)
+		return true;
+
+	/* l3index always overrides non-l3index */
+	if (old->l3index && new->l3index == 0)
+		return false;
+	if (old->l3index == 0 && new->l3index)
+		return true;
+
+	return false;
+}
+
 static struct tcp_authopt_key_info *tcp_authopt_lookup_send(struct netns_tcp_authopt *net,
    						    const struct sock *addr_sk,
    						    int send_id)
 {
    struct tcp_authopt_key_info *result = NULL;
    struct tcp_authopt_key_info *key;
+	int l3index = -1;
hlist_for_each_entry_rcu(key, &net->head, node, 0) {
    	if (send_id >= 0 && key->send_id != send_id)
    		continue;
    	if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND)
    		if (!tcp_authopt_key_match_sk_addr(key, addr_sk))
    			continue;
-		if (result && net_ratelimit())
-			pr_warn("ambiguous tcp authentication keys configured for send\n");
-		result = key;
+		if (key->flags & TCP_AUTHOPT_KEY_IFINDEX) {
+			if (l3index < 0)
+				l3index = l3mdev_master_ifindex_by_index(sock_net(addr_sk),
+									 addr_sk->sk_bound_dev_if);
+			if (l3index != key->l3index)
+				continue;
+		}
+		if (better_key_match(result, key))
+			result = key;
+		else if (result)
+			net_warn_ratelimited("ambiguous tcp authentication keys configured for send\n");
    }
return result;
 }
@@ -578,19 +606,21 @@ int tcp_get_authopt_val(struct sock *sk, struct tcp_authopt *opt)
 }
#define TCP_AUTHOPT_KEY_KNOWN_FLAGS ( \
    TCP_AUTHOPT_KEY_DEL | \
    TCP_AUTHOPT_KEY_EXCLUDE_OPTS | \
-	TCP_AUTHOPT_KEY_ADDR_BIND)
+	TCP_AUTHOPT_KEY_ADDR_BIND | \
+	TCP_AUTHOPT_KEY_IFINDEX)
int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
 {
    struct tcp_authopt_key opt;
    struct tcp_authopt_info *info;
    struct tcp_authopt_key_info *key_info, *old_key_info;
    struct netns_tcp_authopt *net = sock_net_tcp_authopt(sk);
    struct tcp_authopt_alg_imp *alg;
+	int l3index = 0;
    int err;
sock_owned_by_me(sk);
    err = check_sysctl_tcp_authopt();
    if (err)
@@ -641,10 +671,24 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
    	return -EINVAL;
    err = tcp_authopt_alg_require(alg);
    if (err)
    	return err;
+	/* check ifindex is valid (zero is always valid) */
+	if (opt.flags & TCP_AUTHOPT_KEY_IFINDEX && opt.ifindex) {
+		struct net_device *dev;
+
+		rcu_read_lock();
+		dev = dev_get_by_index_rcu(sock_net(sk), opt.ifindex);
+		if (dev && netif_is_l3_master(dev))
+			l3index = dev->ifindex;
+		rcu_read_unlock();
+
+		if (!l3index)
+			return -EINVAL;
+	}
+
    key_info = sock_kmalloc(sk, sizeof(*key_info), GFP_KERNEL | __GFP_ZERO);
    if (!key_info)
    	return -ENOMEM;
    mutex_lock(&net->mutex);
    kref_init(&key_info->ref);
@@ -660,10 +704,11 @@ int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
    key_info->alg_id = opt.alg;
    key_info->alg = alg;
    key_info->keylen = opt.keylen;
    memcpy(key_info->key, opt.key, opt.keylen);
    memcpy(&key_info->addr, &opt.addr, sizeof(key_info->addr));
+	key_info->l3index = l3index;
    hlist_add_head_rcu(&key_info->node, &net->head);
    mutex_unlock(&net->mutex);
return 0;
 }
@@ -1423,21 +1468,37 @@ static struct tcp_authopt_key_info *tcp_authopt_lookup_recv(struct sock *sk,
    						    int recv_id,
    						    bool *anykey)
 {
    struct tcp_authopt_key_info *result = NULL;
    struct tcp_authopt_key_info *key;
+	int l3index = -1;
*anykey = false;
    /* multiple matches will cause occasional failures */
    hlist_for_each_entry_rcu(key, &net->head, node, 0) {
    	if (key->flags & TCP_AUTHOPT_KEY_ADDR_BIND &&
    	    !tcp_authopt_key_match_skb_addr(key, skb))
    		continue;
+		if (key->flags & TCP_AUTHOPT_KEY_IFINDEX) {
+			if (l3index < 0) {
+				if (skb->protocol == htons(ETH_P_IP)) {
+					l3index = inet_sdif(skb) ? inet_iif(skb) : 0;
+				} else if (skb->protocol == htons(ETH_P_IPV6)) {
+					l3index = inet6_sdif(skb) ? inet6_iif(skb) : 0;
+				} else {
+					WARN_ONCE(1, "unexpected skb->protocol=%x", skb->protocol);
+					continue;
+				}
+			}
+
+			if (l3index != key->l3index)
+				continue;
+		}
    	*anykey = true;
    	if (recv_id >= 0 && key->recv_id != recv_id)
    		continue;
-		if (!result)
+		if (better_key_match(result, key))
    		result = key;
    	else if (result)
    		net_warn_ratelimited("ambiguous tcp authentication keys configured for recv\n");
    }
-- 
2.25.1


    

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[PATCH v4 13/19] tcp: authopt: Add initial l3index support