linux/net/ipv4/tcp_ao.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * INET		An implementation of the TCP Authentication Option (TCP-AO).
 *		See RFC5925.
 *
 * Authors:	Dmitry Safonov <dima@arista.com>
 *		Francesco Ruggeri <fruggeri@arista.com>
 *		Salam Noureddine <noureddine@arista.com>
 */
#define pr_fmt(fmt) "TCP: " fmt

#include <crypto/hash.h>
#include <linux/inetdevice.h>
#include <linux/tcp.h>

#include <net/tcp.h>
#include <net/ipv6.h>

/* Optimized version of tcp_ao_do_lookup(): only for sockets for which
 * it's known that the keys in ao_info are matching peer's
 * family/address/VRF/etc.
 */
static struct tcp_ao_key *tcp_ao_established_key(struct tcp_ao_info *ao,
						 int sndid, int rcvid)
{
	struct tcp_ao_key *key;

	hlist_for_each_entry_rcu(key, &ao->head, node) {
		if ((sndid >= 0 && key->sndid != sndid) ||
		    (rcvid >= 0 && key->rcvid != rcvid))
			continue;
		return key;
	}

	return NULL;
}

static int ipv4_prefix_cmp(const struct in_addr *addr1,
			   const struct in_addr *addr2,
			   unsigned int prefixlen)
{
	__be32 mask = inet_make_mask(prefixlen);
	__be32 a1 = addr1->s_addr & mask;
	__be32 a2 = addr2->s_addr & mask;

	if (a1 == a2)
		return 0;
	return memcmp(&a1, &a2, sizeof(a1));
}

static int __tcp_ao_key_cmp(const struct tcp_ao_key *key,
			    const union tcp_ao_addr *addr, u8 prefixlen,
			    int family, int sndid, int rcvid)
{
	if (sndid >= 0 && key->sndid != sndid)
		return (key->sndid > sndid) ? 1 : -1;
	if (rcvid >= 0 && key->rcvid != rcvid)
		return (key->rcvid > rcvid) ? 1 : -1;

	if (family == AF_UNSPEC)
		return 0;
	if (key->family != family)
		return (key->family > family) ? 1 : -1;

	if (family == AF_INET) {
		if (ntohl(key->addr.a4.s_addr) == INADDR_ANY)
			return 0;
		if (ntohl(addr->a4.s_addr) == INADDR_ANY)
			return 0;
		return ipv4_prefix_cmp(&key->addr.a4, &addr->a4, prefixlen);
#if IS_ENABLED(CONFIG_IPV6)
	} else {
		if (ipv6_addr_any(&key->addr.a6) || ipv6_addr_any(&addr->a6))
			return 0;
		if (ipv6_prefix_equal(&key->addr.a6, &addr->a6, prefixlen))
			return 0;
		return memcmp(&key->addr.a6, &addr->a6, sizeof(addr->a6));
#endif
	}
	return -1;
}

static int tcp_ao_key_cmp(const struct tcp_ao_key *key,
			  const union tcp_ao_addr *addr, u8 prefixlen,
			  int family, int sndid, int rcvid)
{
#if IS_ENABLED(CONFIG_IPV6)
	if (family == AF_INET6 && ipv6_addr_v4mapped(&addr->a6)) {
		__be32 addr4 = addr->a6.s6_addr32[3];

		return __tcp_ao_key_cmp(key, (union tcp_ao_addr *)&addr4,
					prefixlen, AF_INET, sndid, rcvid);
	}
#endif
	return __tcp_ao_key_cmp(key, addr, prefixlen, family, sndid, rcvid);
}

static struct tcp_ao_key *__tcp_ao_do_lookup(const struct sock *sk,
		const union tcp_ao_addr *addr, int family, u8 prefix,
		int sndid, int rcvid)
{
	struct tcp_ao_key *key;
	struct tcp_ao_info *ao;

	ao = rcu_dereference_check(tcp_sk(sk)->ao_info,
				   lockdep_sock_is_held(sk));
	if (!ao)
		return NULL;

	hlist_for_each_entry_rcu(key, &ao->head, node) {
		u8 prefixlen = min(prefix, key->prefixlen);

		if (!tcp_ao_key_cmp(key, addr, prefixlen, family, sndid, rcvid))
			return key;
	}
	return NULL;
}

static struct tcp_ao_info *tcp_ao_alloc_info(gfp_t flags)
{
	struct tcp_ao_info *ao;

	ao = kzalloc(sizeof(*ao), flags);
	if (!ao)
		return NULL;
	INIT_HLIST_HEAD(&ao->head);

	return ao;
}

static void tcp_ao_link_mkt(struct tcp_ao_info *ao, struct tcp_ao_key *mkt)
{
	hlist_add_head_rcu(&mkt->node, &ao->head);
}

static void tcp_ao_key_free_rcu(struct rcu_head *head)
{
	struct tcp_ao_key *key = container_of(head, struct tcp_ao_key, rcu);

	tcp_sigpool_release(key->tcp_sigpool_id);
	kfree_sensitive(key);
}

void tcp_ao_destroy_sock(struct sock *sk)
{
	struct tcp_ao_info *ao;
	struct tcp_ao_key *key;
	struct hlist_node *n;

	ao = rcu_dereference_protected(tcp_sk(sk)->ao_info, 1);
	tcp_sk(sk)->ao_info = NULL;

	if (!ao)
		return;

	hlist_for_each_entry_safe(key, n, &ao->head, node) {
		hlist_del_rcu(&key->node);
		atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
		call_rcu(&key->rcu, tcp_ao_key_free_rcu);
	}

	kfree_rcu(ao, rcu);
}

static bool tcp_ao_can_set_current_rnext(struct sock *sk)
{
	/* There aren't current/rnext keys on TCP_LISTEN sockets */
	if (sk->sk_state == TCP_LISTEN)
		return false;
	return true;
}

static int tcp_ao_verify_ipv4(struct sock *sk, struct tcp_ao_add *cmd,
			      union tcp_ao_addr **addr)
{
	struct sockaddr_in *sin = (struct sockaddr_in *)&cmd->addr;
	struct inet_sock *inet = inet_sk(sk);

	if (sin->sin_family != AF_INET)
		return -EINVAL;

	/* Currently matching is not performed on port (or port ranges) */
	if (sin->sin_port != 0)
		return -EINVAL;

	/* Check prefix and trailing 0's in addr */
	if (cmd->prefix != 0) {
		__be32 mask;

		if (ntohl(sin->sin_addr.s_addr) == INADDR_ANY)
			return -EINVAL;
		if (cmd->prefix > 32)
			return -EINVAL;

		mask = inet_make_mask(cmd->prefix);
		if (sin->sin_addr.s_addr & ~mask)
			return -EINVAL;

		/* Check that MKT address is consistent with socket */
		if (ntohl(inet->inet_daddr) != INADDR_ANY &&
		    (inet->inet_daddr & mask) != sin->sin_addr.s_addr)
			return -EINVAL;
	} else {
		if (ntohl(sin->sin_addr.s_addr) != INADDR_ANY)
			return -EINVAL;
	}

	*addr = (union tcp_ao_addr *)&sin->sin_addr;
	return 0;
}

static int tcp_ao_parse_crypto(struct tcp_ao_add *cmd, struct tcp_ao_key *key)
{
	unsigned int syn_tcp_option_space;
	bool is_kdf_aes_128_cmac = false;
	struct crypto_ahash *tfm;
	struct tcp_sigpool hp;
	void *tmp_key = NULL;
	int err;

	/* RFC5926, 3.1.1.2. KDF_AES_128_CMAC */
	if (!strcmp("cmac(aes128)", cmd->alg_name)) {
		strscpy(cmd->alg_name, "cmac(aes)", sizeof(cmd->alg_name));
		is_kdf_aes_128_cmac = (cmd->keylen != 16);
		tmp_key = kmalloc(cmd->keylen, GFP_KERNEL);
		if (!tmp_key)
			return -ENOMEM;
	}

	key->maclen = cmd->maclen ?: 12; /* 12 is the default in RFC5925 */

	/* Check: maclen + tcp-ao header <= (MAX_TCP_OPTION_SPACE - mss
	 *					- tstamp - wscale - sackperm),
	 * see tcp_syn_options(), tcp_synack_options(), commit 33ad798c924b.
	 *
	 * In order to allow D-SACK with TCP-AO, the header size should be:
	 * (MAX_TCP_OPTION_SPACE - TCPOLEN_TSTAMP_ALIGNED
	 *			- TCPOLEN_SACK_BASE_ALIGNED
	 *			- 2 * TCPOLEN_SACK_PERBLOCK) = 8 (maclen = 4),
	 * see tcp_established_options().
	 *
	 * RFC5925, 2.2:
	 * Typical MACs are 96-128 bits (12-16 bytes), but any length
	 * that fits in the header of the segment being authenticated
	 * is allowed.
	 *
	 * RFC5925, 7.6:
	 * TCP-AO continues to consume 16 bytes in non-SYN segments,
	 * leaving a total of 24 bytes for other options, of which
	 * the timestamp consumes 10.  This leaves 14 bytes, of which 10
	 * are used for a single SACK block. When two SACK blocks are used,
	 * such as to handle D-SACK, a smaller TCP-AO MAC would be required
	 * to make room for the additional SACK block (i.e., to leave 18
	 * bytes for the D-SACK variant of the SACK option) [RFC2883].
	 * Note that D-SACK is not supportable in TCP MD5 in the presence
	 * of timestamps, because TCP MD5’s MAC length is fixed and too
	 * large to leave sufficient option space.
	 */
	syn_tcp_option_space = MAX_TCP_OPTION_SPACE;
	syn_tcp_option_space -= TCPOLEN_TSTAMP_ALIGNED;
	syn_tcp_option_space -= TCPOLEN_WSCALE_ALIGNED;
	syn_tcp_option_space -= TCPOLEN_SACKPERM_ALIGNED;
	if (tcp_ao_len(key) > syn_tcp_option_space) {
		err = -EMSGSIZE;
		goto err_kfree;
	}

	key->keylen = cmd->keylen;
	memcpy(key->key, cmd->key, cmd->keylen);

	err = tcp_sigpool_start(key->tcp_sigpool_id, &hp);
	if (err)
		goto err_kfree;

	tfm = crypto_ahash_reqtfm(hp.req);
	if (is_kdf_aes_128_cmac) {
		void *scratch = hp.scratch;
		struct scatterlist sg;

		memcpy(tmp_key, cmd->key, cmd->keylen);
		sg_init_one(&sg, tmp_key, cmd->keylen);

		/* Using zero-key of 16 bytes as described in RFC5926 */
		memset(scratch, 0, 16);
		err = crypto_ahash_setkey(tfm, scratch, 16);
		if (err)
			goto err_pool_end;

		err = crypto_ahash_init(hp.req);
		if (err)
			goto err_pool_end;

		ahash_request_set_crypt(hp.req, &sg, key->key, cmd->keylen);
		err = crypto_ahash_update(hp.req);
		if (err)
			goto err_pool_end;

		err |= crypto_ahash_final(hp.req);
		if (err)
			goto err_pool_end;
		key->keylen = 16;
	}

	err = crypto_ahash_setkey(tfm, key->key, key->keylen);
	if (err)
		goto err_pool_end;

	tcp_sigpool_end(&hp);
	kfree_sensitive(tmp_key);

	if (tcp_ao_maclen(key) > key->digest_size)
		return -EINVAL;

	return 0;

err_pool_end:
	tcp_sigpool_end(&hp);
err_kfree:
	kfree_sensitive(tmp_key);
	return err;
}

#if IS_ENABLED(CONFIG_IPV6)
static int tcp_ao_verify_ipv6(struct sock *sk, struct tcp_ao_add *cmd,
			      union tcp_ao_addr **paddr,
			      unsigned short int *family)
{
	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd->addr;
	struct in6_addr *addr = &sin6->sin6_addr;
	u8 prefix = cmd->prefix;

	if (sin6->sin6_family != AF_INET6)
		return -EINVAL;

	/* Currently matching is not performed on port (or port ranges) */
	if (sin6->sin6_port != 0)
		return -EINVAL;

	/* Check prefix and trailing 0's in addr */
	if (cmd->prefix != 0 && ipv6_addr_v4mapped(addr)) {
		__be32 addr4 = addr->s6_addr32[3];
		__be32 mask;

		if (prefix > 32 || ntohl(addr4) == INADDR_ANY)
			return -EINVAL;

		mask = inet_make_mask(prefix);
		if (addr4 & ~mask)
			return -EINVAL;

		/* Check that MKT address is consistent with socket */
		if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
			__be32 daddr4 = sk->sk_v6_daddr.s6_addr32[3];

			if (!ipv6_addr_v4mapped(&sk->sk_v6_daddr))
				return -EINVAL;
			if ((daddr4 & mask) != addr4)
				return -EINVAL;
		}

		*paddr = (union tcp_ao_addr *)&addr->s6_addr32[3];
		*family = AF_INET;
		return 0;
	} else if (cmd->prefix != 0) {
		struct in6_addr pfx;

		if (ipv6_addr_any(addr) || prefix > 128)
			return -EINVAL;

		ipv6_addr_prefix(&pfx, addr, prefix);
		if (ipv6_addr_cmp(&pfx, addr))
			return -EINVAL;

		/* Check that MKT address is consistent with socket */
		if (!ipv6_addr_any(&sk->sk_v6_daddr) &&
		    !ipv6_prefix_equal(&sk->sk_v6_daddr, addr, prefix))

			return -EINVAL;
	} else {
		if (!ipv6_addr_any(addr))
			return -EINVAL;
	}

	*paddr = (union tcp_ao_addr *)addr;
	return 0;
}
#else
static int tcp_ao_verify_ipv6(struct sock *sk, struct tcp_ao_add *cmd,
			      union tcp_ao_addr **paddr,
			      unsigned short int *family)
{
	return -EOPNOTSUPP;
}
#endif

static struct tcp_ao_info *setsockopt_ao_info(struct sock *sk)
{
	if (sk_fullsock(sk)) {
		return rcu_dereference_protected(tcp_sk(sk)->ao_info,
						 lockdep_sock_is_held(sk));
	}
	return ERR_PTR(-ESOCKTNOSUPPORT);
}

#define TCP_AO_KEYF_ALL		(0)

static struct tcp_ao_key *tcp_ao_key_alloc(struct sock *sk,
					   struct tcp_ao_add *cmd)
{
	const char *algo = cmd->alg_name;
	unsigned int digest_size;
	struct crypto_ahash *tfm;
	struct tcp_ao_key *key;
	struct tcp_sigpool hp;
	int err, pool_id;
	size_t size;

	/* Force null-termination of alg_name */
	cmd->alg_name[ARRAY_SIZE(cmd->alg_name) - 1] = '\0';

	/* RFC5926, 3.1.1.2. KDF_AES_128_CMAC */
	if (!strcmp("cmac(aes128)", algo))
		algo = "cmac(aes)";

	/* Full TCP header (th->doff << 2) should fit into scratch area,
	 * see tcp_ao_hash_header().
	 */
	pool_id = tcp_sigpool_alloc_ahash(algo, 60);
	if (pool_id < 0)
		return ERR_PTR(pool_id);

	err = tcp_sigpool_start(pool_id, &hp);
	if (err)
		goto err_free_pool;

	tfm = crypto_ahash_reqtfm(hp.req);
	if (crypto_ahash_alignmask(tfm) > TCP_AO_KEY_ALIGN) {
		err = -EOPNOTSUPP;
		goto err_pool_end;
	}
	digest_size = crypto_ahash_digestsize(tfm);
	tcp_sigpool_end(&hp);

	size = sizeof(struct tcp_ao_key) + (digest_size << 1);
	key = sock_kmalloc(sk, size, GFP_KERNEL);
	if (!key) {
		err = -ENOMEM;
		goto err_free_pool;
	}

	key->tcp_sigpool_id = pool_id;
	key->digest_size = digest_size;
	return key;

err_pool_end:
	tcp_sigpool_end(&hp);
err_free_pool:
	tcp_sigpool_release(pool_id);
	return ERR_PTR(err);
}

static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
			  sockptr_t optval, int optlen)
{
	struct tcp_ao_info *ao_info;
	union tcp_ao_addr *addr;
	struct tcp_ao_key *key;
	struct tcp_ao_add cmd;
	bool first = false;
	int ret;

	if (optlen < sizeof(cmd))
		return -EINVAL;

	ret = copy_struct_from_sockptr(&cmd, sizeof(cmd), optval, optlen);
	if (ret)
		return ret;

	if (cmd.keylen > TCP_AO_MAXKEYLEN)
		return -EINVAL;

	if (cmd.reserved != 0 || cmd.reserved2 != 0)
		return -EINVAL;

	if (family == AF_INET)
		ret = tcp_ao_verify_ipv4(sk, &cmd, &addr);
	else
		ret = tcp_ao_verify_ipv6(sk, &cmd, &addr, &family);
	if (ret)
		return ret;

	if (cmd.keyflags & ~TCP_AO_KEYF_ALL)
		return -EINVAL;

	if (cmd.set_current || cmd.set_rnext) {
		if (!tcp_ao_can_set_current_rnext(sk))
			return -EINVAL;
	}

	ao_info = setsockopt_ao_info(sk);
	if (IS_ERR(ao_info))
		return PTR_ERR(ao_info);

	if (!ao_info) {
		ao_info = tcp_ao_alloc_info(GFP_KERNEL);
		if (!ao_info)
			return -ENOMEM;
		first = true;
	} else {
		/* Check that neither RecvID nor SendID match any
		 * existing key for the peer, RFC5925 3.1:
		 * > The IDs of MKTs MUST NOT overlap where their
		 * > TCP connection identifiers overlap.
		 */
		if (__tcp_ao_do_lookup(sk, addr, family,
				       cmd.prefix, -1, cmd.rcvid))
			return -EEXIST;
		if (__tcp_ao_do_lookup(sk, addr, family,
				       cmd.prefix, cmd.sndid, -1))
			return -EEXIST;
	}

	key = tcp_ao_key_alloc(sk, &cmd);
	if (IS_ERR(key)) {
		ret = PTR_ERR(key);
		goto err_free_ao;
	}

	INIT_HLIST_NODE(&key->node);
	memcpy(&key->addr, addr, (family == AF_INET) ? sizeof(struct in_addr) :
						       sizeof(struct in6_addr));
	key->prefixlen	= cmd.prefix;
	key->family	= family;
	key->keyflags	= cmd.keyflags;
	key->sndid	= cmd.sndid;
	key->rcvid	= cmd.rcvid;

	ret = tcp_ao_parse_crypto(&cmd, key);
	if (ret < 0)
		goto err_free_sock;

	tcp_ao_link_mkt(ao_info, key);
	if (first) {
		sk_gso_disable(sk);
		rcu_assign_pointer(tcp_sk(sk)->ao_info, ao_info);
	}

	if (cmd.set_current)
		WRITE_ONCE(ao_info->current_key, key);
	if (cmd.set_rnext)
		WRITE_ONCE(ao_info->rnext_key, key);
	return 0;

err_free_sock:
	atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
	tcp_sigpool_release(key->tcp_sigpool_id);
	kfree_sensitive(key);
err_free_ao:
	if (first)
		kfree(ao_info);
	return ret;
}

static int tcp_ao_delete_key(struct sock *sk, struct tcp_ao_info *ao_info,
			     struct tcp_ao_key *key,
			     struct tcp_ao_key *new_current,
			     struct tcp_ao_key *new_rnext)
{
	int err;

	hlist_del_rcu(&key->node);

	/* At this moment another CPU could have looked this key up
	 * while it was unlinked from the list. Wait for RCU grace period,
	 * after which the key is off-list and can't be looked up again;
	 * the rx path [just before RCU came] might have used it and set it
	 * as current_key (very unlikely).
	 */
	synchronize_rcu();
	if (new_current)
		WRITE_ONCE(ao_info->current_key, new_current);
	if (new_rnext)
		WRITE_ONCE(ao_info->rnext_key, new_rnext);

	if (unlikely(READ_ONCE(ao_info->current_key) == key ||
		     READ_ONCE(ao_info->rnext_key) == key)) {
		err = -EBUSY;
		goto add_key;
	}

	atomic_sub(tcp_ao_sizeof_key(key), &sk->sk_omem_alloc);
	call_rcu(&key->rcu, tcp_ao_key_free_rcu);

	return 0;
add_key:
	hlist_add_head_rcu(&key->node, &ao_info->head);
	return err;
}

static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family,
			  sockptr_t optval, int optlen)
{
	struct tcp_ao_key *key, *new_current = NULL, *new_rnext = NULL;
	struct tcp_ao_info *ao_info;
	union tcp_ao_addr *addr;
	struct tcp_ao_del cmd;
	int addr_len;
	__u8 prefix;
	u16 port;
	int err;

	if (optlen < sizeof(cmd))
		return -EINVAL;

	err = copy_struct_from_sockptr(&cmd, sizeof(cmd), optval, optlen);
	if (err)
		return err;

	if (cmd.reserved != 0 || cmd.reserved2 != 0)
		return -EINVAL;

	if (cmd.set_current || cmd.set_rnext) {
		if (!tcp_ao_can_set_current_rnext(sk))
			return -EINVAL;
	}

	ao_info = setsockopt_ao_info(sk);
	if (IS_ERR(ao_info))
		return PTR_ERR(ao_info);
	if (!ao_info)
		return -ENOENT;

	/* For sockets in TCP_CLOSED it's possible set keys that aren't
	 * matching the future peer (address/VRF/etc),
	 * tcp_ao_connect_init() will choose a correct matching MKT
	 * if there's any.
	 */
	if (cmd.set_current) {
		new_current = tcp_ao_established_key(ao_info, cmd.current_key, -1);
		if (!new_current)
			return -ENOENT;
	}
	if (cmd.set_rnext) {
		new_rnext = tcp_ao_established_key(ao_info, -1, cmd.rnext);
		if (!new_rnext)
			return -ENOENT;
	}

	if (family == AF_INET) {
		struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.addr;

		addr = (union tcp_ao_addr *)&sin->sin_addr;
		addr_len = sizeof(struct in_addr);
		port = ntohs(sin->sin_port);
	} else {
		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd.addr;
		struct in6_addr *addr6 = &sin6->sin6_addr;

		if (ipv6_addr_v4mapped(addr6)) {
			addr = (union tcp_ao_addr *)&addr6->s6_addr32[3];
			addr_len = sizeof(struct in_addr);
			family = AF_INET;
		} else {
			addr = (union tcp_ao_addr *)addr6;
			addr_len = sizeof(struct in6_addr);
		}
		port = ntohs(sin6->sin6_port);
	}
	prefix = cmd.prefix;

	/* Currently matching is not performed on port (or port ranges) */
	if (port != 0)
		return -EINVAL;

	/* We could choose random present key here for current/rnext
	 * but that's less predictable. Let's be strict and don't
	 * allow removing a key that's in use. RFC5925 doesn't
	 * specify how-to coordinate key removal, but says:
	 * "It is presumed that an MKT affecting a particular
	 * connection cannot be destroyed during an active connection"
	 */
	hlist_for_each_entry_rcu(key, &ao_info->head, node) {
		if (cmd.sndid != key->sndid ||
		    cmd.rcvid != key->rcvid)
			continue;

		if (family != key->family ||
		    prefix != key->prefixlen ||
		    memcmp(addr, &key->addr, addr_len))
			continue;

		if (key == new_current || key == new_rnext)
			continue;

		return tcp_ao_delete_key(sk, ao_info, key,
					  new_current, new_rnext);
	}
	return -ENOENT;
}

static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family,
			   sockptr_t optval, int optlen)
{
	struct tcp_ao_key *new_current = NULL, *new_rnext = NULL;
	struct tcp_ao_info *ao_info;
	struct tcp_ao_info_opt cmd;
	bool first = false;
	int err;

	if (optlen < sizeof(cmd))
		return -EINVAL;

	err = copy_struct_from_sockptr(&cmd, sizeof(cmd), optval, optlen);
	if (err)
		return err;

	if (cmd.set_current || cmd.set_rnext) {
		if (!tcp_ao_can_set_current_rnext(sk))
			return -EINVAL;
	}

	if (cmd.reserved != 0)
		return -EINVAL;

	ao_info = setsockopt_ao_info(sk);
	if (IS_ERR(ao_info))
		return PTR_ERR(ao_info);
	if (!ao_info) {
		ao_info = tcp_ao_alloc_info(GFP_KERNEL);
		if (!ao_info)
			return -ENOMEM;
		first = true;
	}

	/* For sockets in TCP_CLOSED it's possible set keys that aren't
	 * matching the future peer (address/port/VRF/etc),
	 * tcp_ao_connect_init() will choose a correct matching MKT
	 * if there's any.
	 */
	if (cmd.set_current) {
		new_current = tcp_ao_established_key(ao_info, cmd.current_key, -1);
		if (!new_current) {
			err = -ENOENT;
			goto out;
		}
	}
	if (cmd.set_rnext) {
		new_rnext = tcp_ao_established_key(ao_info, -1, cmd.rnext);
		if (!new_rnext) {
			err = -ENOENT;
			goto out;
		}
	}

	ao_info->ao_required = cmd.ao_required;
	if (new_current)
		WRITE_ONCE(ao_info->current_key, new_current);
	if (new_rnext)
		WRITE_ONCE(ao_info->rnext_key, new_rnext);
	if (first) {
		sk_gso_disable(sk);
		rcu_assign_pointer(tcp_sk(sk)->ao_info, ao_info);
	}
	return 0;
out:
	if (first)
		kfree(ao_info);
	return err;
}

int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
		 sockptr_t optval, int optlen)
{
	if (WARN_ON_ONCE(family != AF_INET && family != AF_INET6))
		return -EAFNOSUPPORT;

	switch (cmd) {
	case TCP_AO_ADD_KEY:
		return tcp_ao_add_cmd(sk, family, optval, optlen);
	case TCP_AO_DEL_KEY:
		return tcp_ao_del_cmd(sk, family, optval, optlen);
	case TCP_AO_INFO:
		return tcp_ao_info_cmd(sk, family, optval, optlen);
	default:
		WARN_ON_ONCE(1);
		return -EINVAL;
	}
}

int tcp_v4_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen)
{
	return tcp_parse_ao(sk, cmd, AF_INET, optval, optlen);
}