[PATCH v5 13/20] tcp: authopt: Add initial l3index support

From: Leonard Crestez
Date: Mon Jan 24 2022 - 07:15:16 EST

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@xxxxxxxxx>
---
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 c00b23f1e5af..3d2c4283923f 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>

@@ -264,10 +265,14 @@ 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;
@@ -333,26 +338,49 @@ 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;
}

@@ -583,19 +611,21 @@ 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)
@@ -646,10 +676,24 @@ 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);
@@ -665,10 +709,11 @@ 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;
}
@@ -1455,21 +1500,37 @@ 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