Re: [RFC] tcp: Initial support for RFC5925 auth option

Kuniyuki Iwashima
2021-07-19T17:17:29Z

From: Leonard Crestez <cdleonard@gmail.com>
Date: Mon, 19 Jul 2021 14:24:46 +0300
> This is similar to TCP MD5 in functionality but it's sufficiently
> different that userspace interface and wire formats are incompatible.
> Compared to TCP-MD5 more algorithms are supported and multiple keys can
> be used on the same connection but there is still no negotiation
> mechanism.
>
> Expected use-case is protecting long-duration BGP/LDP connections
> between routers using pre-shared keys.
>
> This is an early version which focuses on getting the correct
> signature bits on the wire in a way that can interoperate with other
> implementations. Major issues still need to be solved:
>
> * Lockdep warnings (incorrect context for initializing shash)
> * Support for aes-128-cmac-96
> * Binding keys to addresses and/or interfaces similar to md5
> * Sequence Number Extension
>
> A small test suite is here: https://github.com/cdleonard/tcp-authopt-test
> The tests work by establishing loopback TCP connections, capturing
> packets with scapy and validating signatures.
>
> Changes for yabgp are here:
> https://github.com/cdleonard/yabgp/commits/tcp_authopt
> The patched version of yabgp can establish a BGP session protected by
> TCP Authentication Option with a Cisco IOS-XR router.
>
> I'm especially interested in feedback regarding ABI and testing.
>
> Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
>
> ---
>
> Allocating shash requires user context but holding a struct tfm in
> tcp_authopt_key_info allocated by tcp_set_authopt_key doesn't work
> because when a server handshake is succesful the server socket needs to
> copy the keys of the listen socket in softirq context.
>
> Sharing the crypto_shash tfm between listen and server sockets doesn't
> work well either because keys for each connection (and each syn packet)
> are different and the hmac or cmac key is per-tfm rather than per
> shash_desc. The server sockets would need locking to access their shared
> tfm.
>
> Simplest solution would be to allocate one shash for each CPU and borrow
> it for each hashing operation. TCP-MD5 allocates one ahash globally but
> that can't work for hmac/cmac because of setkey.
>
> Signed-off-by: Leonard Crestez <cdleonard@gmail.com>
> ---
> include/linux/tcp.h | 6 +
> include/net/tcp.h | 1 +
> include/net/tcp_authopt.h | 103 ++++++
> include/uapi/linux/snmp.h | 1 +
> include/uapi/linux/tcp.h | 40 +++
> net/ipv4/Kconfig | 14 +
> net/ipv4/Makefile | 1 +
> net/ipv4/proc.c | 1 +
> net/ipv4/tcp.c | 7 +
> net/ipv4/tcp_authopt.c | 718 ++++++++++++++++++++++++++++++++++++++
> net/ipv4/tcp_input.c | 17 +
> net/ipv4/tcp_ipv4.c | 5 +
> net/ipv4/tcp_minisocks.c | 2 +
> net/ipv4/tcp_output.c | 65 +++-
> 14 files changed, 980 insertions(+), 1 deletion(-)
> create mode 100644 include/net/tcp_authopt.h
> create mode 100644 net/ipv4/tcp_authopt.c
>
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 48d8a363319e..cfddfc720b00 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -140,10 +140,12 @@ struct tcp_request_sock {
> static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
> {
> return (struct tcp_request_sock *)req;
> }
>
> +struct tcp_authopt_info;
> +
> struct tcp_sock {
> /* inet_connection_sock has to be the first member of tcp_sock */
> struct inet_connection_sock inet_conn;
> u16 tcp_header_len; /* Bytes of tcp header to send */
> u16 gso_segs; /* Max number of segs per GSO packet */
> @@ -403,10 +405,14 @@ struct tcp_sock {
>
> /* TCP MD5 Signature Option information */
> struct tcp_md5sig_info __rcu *md5sig_info;
> #endif
>
> +#ifdef CONFIG_TCP_AUTHOPT
> + struct tcp_authopt_info __rcu *authopt_info;
> +#endif
> +
> /* TCP fastopen related information */
> struct tcp_fastopen_request *fastopen_req;
> /* fastopen_rsk points to request_sock that resulted in this big
> * socket. Used to retransmit SYNACKs etc.
> */
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 17df9b047ee4..767611fd5ec3 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -182,10 +182,11 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
> #define TCPOPT_WINDOW 3 /* Window scaling */
> #define TCPOPT_SACK_PERM 4 /* SACK Permitted */
> #define TCPOPT_SACK 5 /* SACK Block */
> #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
> #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
> +#define TCPOPT_AUTHOPT 29 /* Auth Option (RFC5925) */
> #define TCPOPT_MPTCP 30 /* Multipath TCP (RFC6824) */
> #define TCPOPT_FASTOPEN 34 /* Fast open (RFC7413) */
> #define TCPOPT_EXP 254 /* Experimental */
> /* Magic number to be after the option value for sharing TCP
> * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
> diff --git a/include/net/tcp_authopt.h b/include/net/tcp_authopt.h
> new file mode 100644
> index 000000000000..aaab5c955984
> --- /dev/null
> +++ b/include/net/tcp_authopt.h
> @@ -0,0 +1,103 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _LINUX_TCP_AUTHOPT_H
> +#define _LINUX_TCP_AUTHOPT_H
> +
> +#include <uapi/linux/tcp.h>
> +
> +/* Representation of a Master Key Tuple as per RFC5925 */
> +struct tcp_authopt_key_info {
> + struct hlist_node node;
> + /* Local identifier */
> + u32 local_id;
> + u32 flags;
> + /* Wire identifiers */
> + u8 send_id, recv_id;
> + u8 alg;
> + u8 keylen;
> + u8 key[TCP_AUTHOPT_MAXKEYLEN];
> + u8 maclen;
> + u8 traffic_key_len;
> + struct rcu_head rcu;
> +};
> +
> +/* Per-socket information regarding tcp_authopt */
> +struct tcp_authopt_info {
> + struct hlist_head head;
> + u32 local_send_id;
> + u32 src_isn;
> + u32 dst_isn;
> + u8 rnextkeyid;
> + struct rcu_head rcu;
> +};
> +
> +#ifdef CONFIG_TCP_AUTHOPT
> +struct tcp_authopt_key_info *tcp_authopt_key_info_lookup(struct sock *sk, int key_id);
> +void tcp_authopt_clear(struct sock *sk);
> +int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen);
> +int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen);
> +int tcp_authopt_hash(
> + char *hash_location,
> + struct tcp_authopt_key_info *key,
> + struct sock *sk, struct sk_buff *skb);
> +int __tcp_authopt_openreq(struct sock *newsk, const struct sock *oldsk, struct request_sock *req);
> +static inline int tcp_authopt_openreq(
> + struct sock *newsk,
> + const struct sock *oldsk,
> + struct request_sock *req)
> +{
> + if (!rcu_dereference(tcp_sk(oldsk)->authopt_info))

s/rcu_dereference/rcu_access_pointer/

> + return 0;
> + else
> + return __tcp_authopt_openreq(newsk, oldsk, req);

nit: 'else' can be removed.

> +}
> +int __tcp_authopt_inbound_check(
> + struct sock *sk,
> + struct sk_buff *skb,
> + struct tcp_authopt_info *info);
> +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb)
> +{
> + struct tcp_authopt_info *info = rcu_dereference(tcp_sk(sk)->authopt_info);
> +
> + if (info)
> + return __tcp_authopt_inbound_check(sk, skb, info);
> + else
> + return 0;

Same with the above and can be formatted like:

if (!info)
return 0;

return __tcp_authopt_inbound_check(sk, skb, info);

> +}
> +#else
> +static inline struct tcp_authopt_key_info *tcp_authopt_key_info_lookup(
> + struct sock *sk,
> + int key_id)
> +{
> + return NULL;
> +}
> +static inline int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen)
> +{
> + return -ENOPROTOOPT;
> +}
> +static inline void tcp_authopt_clear(struct sock *sk)
> +{
> +}
> +static inline int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
> +{
> + return -ENOPROTOOPT;
> +}
> +static inline int tcp_authopt_hash(
> + char *hash_location,
> + struct tcp_authopt_key_info *key,
> + struct sock *sk, struct sk_buff *skb)
> +{
> + return -EINVAL;
> +}
> +static inline int tcp_authopt_openreq(struct sock *newsk,
> + const struct sock *oldsk,
> + struct request_sock *req)
> +{
> + return 0;
> +}
> +static inline int tcp_authopt_inbound_check(struct sock *sk, struct sk_buff *skb)
> +{
> + return 0;
> +}
> +#endif
> +
> +#endif /* _LINUX_TCP_AUTHOPT_H */
> diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
> index 904909d020e2..1d96030889a1 100644
> --- a/include/uapi/linux/snmp.h
> +++ b/include/uapi/linux/snmp.h
> @@ -290,10 +290,11 @@ enum
> LINUX_MIB_TCPDUPLICATEDATAREHASH, /* TCPDuplicateDataRehash */
> LINUX_MIB_TCPDSACKRECVSEGS, /* TCPDSACKRecvSegs */
> LINUX_MIB_TCPDSACKIGNOREDDUBIOUS, /* TCPDSACKIgnoredDubious */
> LINUX_MIB_TCPMIGRATEREQSUCCESS, /* TCPMigrateReqSuccess */
> LINUX_MIB_TCPMIGRATEREQFAILURE, /* TCPMigrateReqFailure */
> + LINUX_MIB_TCPAUTHOPTFAILURE, /* TCPAuthOptFailure */
> __LINUX_MIB_MAX
> };
>
> /* linux Xfrm mib definitions */
> enum
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index 8fc09e8638b3..30b8ad769871 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -126,10 +126,12 @@ enum {
> #define TCP_INQ 36 /* Notify bytes available to read as a cmsg on read */
>
> #define TCP_CM_INQ TCP_INQ
>
> #define TCP_TX_DELAY 37 /* delay outgoing packets by XX usec */
> +#define TCP_AUTHOPT 38 /* TCP Authentication Option (RFC2385) */
> +#define TCP_AUTHOPT_KEY 39 /* TCP Authentication Option update key (RFC2385) */
>
>
> #define TCP_REPAIR_ON 1
> #define TCP_REPAIR_OFF 0
> #define TCP_REPAIR_OFF_NO_WP -1 /* Turn off without window probes */
> @@ -340,10 +342,48 @@ struct tcp_diag_md5sig {
> __u16 tcpm_keylen;
> __be32 tcpm_addr[4];
> __u8 tcpm_key[TCP_MD5SIG_MAXKEYLEN];
> };
>
> +/* for TCP_AUTHOPT socket option */
> +#define TCP_AUTHOPT_MAXKEYLEN 80
> +
> +#define TCP_AUTHOPT_ALG_HMAC_SHA_1_96 1
> +#define TCP_AUTHOPT_ALG_AES_128_CMAC_96 2
> +
> +/* Per-socket options */
> +struct tcp_authopt {
> + /* No flags currently defined */
> + __u32 flags;
> + /* local_id of preferred output key */
> + __u32 local_send_id;
> +};
> +
> +/* Delete the key by local_id and ignore all fields */
> +#define TCP_AUTHOPT_KEY_DEL (1 << 0)
> +/* Exclude TCP options from signature */
> +#define TCP_AUTHOPT_KEY_EXCLUDE_OPTS (1 << 1)
> +
> +/* Per-key options
> + * Each key is identified by a non-zero local_id which is managed by the application.
> + */
> +struct tcp_authopt_key {
> + /* Mix of TCP_AUTHOPT_KEY_ flags */
> + __u32 flags;
> + /* Local identifier */
> + __u32 local_id;
> + /* SendID on the network */
> + __u8 send_id;
> + /* RecvID on the network */
> + __u8 recv_id;
> + /* One of the TCP_AUTHOPT_ALG_* constant */
> + __u8 alg;
> + /* Length of the key buffer */
> + __u8 keylen;
> + __u8 key[TCP_AUTHOPT_MAXKEYLEN];
> +};
> +
> /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */
>
> #define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1
> struct tcp_zerocopy_receive {
> __u64 address; /* in: address of mapping */
> diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
> index 87983e70f03f..6459f4ea6f1d 100644
> --- a/net/ipv4/Kconfig
> +++ b/net/ipv4/Kconfig
> @@ -740,5 +740,19 @@ config TCP_MD5SIG
> RFC2385 specifies a method of giving MD5 protection to TCP sessions.
> Its main (only?) use is to protect BGP sessions between core routers
> on the Internet.
>
> If unsure, say N.
> +
> +config TCP_AUTHOPT
> + bool "TCP: Authentication Option support (RFC5925)"
> + select CRYPTO
> + select CRYPTO_SHA1
> + select CRYPTO_HMAC
> + select CRYPTO_AES
> + select CRYPTO_CMAC
> + help
> + RFC5925 specifies a new method of giving protection to TCP sessions.
> + Its intended use is to protect BGP sessions between core routers
> + on the Internet. It obsoletes TCP MD5 (RFC2385) but is incompatible.
> +
> + If unsure, say N.
> diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
> index bbdd9c44f14e..d336f32ce177 100644
> --- a/net/ipv4/Makefile
> +++ b/net/ipv4/Makefile
> @@ -59,10 +59,11 @@ obj-$(CONFIG_TCP_CONG_NV) += tcp_nv.o
> obj-$(CONFIG_TCP_CONG_VENO) += tcp_veno.o
> obj-$(CONFIG_TCP_CONG_SCALABLE) += tcp_scalable.o
> obj-$(CONFIG_TCP_CONG_LP) += tcp_lp.o
> obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.o
> obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
> +obj-$(CONFIG_TCP_AUTHOPT) += tcp_authopt.o
> obj-$(CONFIG_NET_SOCK_MSG) += tcp_bpf.o
> obj-$(CONFIG_BPF_SYSCALL) += udp_bpf.o
> obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
>
> obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
> diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
> index b0d3a09dc84e..61dd06f8389c 100644
> --- a/net/ipv4/proc.c
> +++ b/net/ipv4/proc.c
> @@ -295,10 +295,11 @@ static const struct snmp_mib snmp4_net_list[] = {
> SNMP_MIB_ITEM("TcpDuplicateDataRehash", LINUX_MIB_TCPDUPLICATEDATAREHASH),
> SNMP_MIB_ITEM("TCPDSACKRecvSegs", LINUX_MIB_TCPDSACKRECVSEGS),
> SNMP_MIB_ITEM("TCPDSACKIgnoredDubious", LINUX_MIB_TCPDSACKIGNOREDDUBIOUS),
> SNMP_MIB_ITEM("TCPMigrateReqSuccess", LINUX_MIB_TCPMIGRATEREQSUCCESS),
> SNMP_MIB_ITEM("TCPMigrateReqFailure", LINUX_MIB_TCPMIGRATEREQFAILURE),
> + SNMP_MIB_ITEM("TCPAuthOptFailure", LINUX_MIB_TCPAUTHOPTFAILURE),
> SNMP_MIB_SENTINEL
> };
>
> static void icmpmsg_put_line(struct seq_file *seq, unsigned long *vals,
> unsigned short *type, int count)
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 8cb44040ec68..3c29bb579d27 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -271,10 +271,11 @@
>
> #include <net/icmp.h>
> #include <net/inet_common.h>
> #include <net/tcp.h>
> #include <net/mptcp.h>
> +#include <net/tcp_authopt.h>
> #include <net/xfrm.h>
> #include <net/ip.h>
> #include <net/sock.h>
>
> #include <linux/uaccess.h>
> @@ -3573,10 +3574,16 @@ static int do_tcp_setsockopt(struct sock *sk, int level, int optname,
> case TCP_MD5SIG:
> case TCP_MD5SIG_EXT:
> err = tp->af_specific->md5_parse(sk, optname, optval, optlen);
> break;
> #endif
> + case TCP_AUTHOPT:
> + err = tcp_set_authopt(sk, optval, optlen);
> + break;
> + case TCP_AUTHOPT_KEY:
> + err = tcp_set_authopt_key(sk, optval, optlen);
> + break;
> case TCP_USER_TIMEOUT:
> /* Cap the max time in ms TCP will retry or probe the window
> * before giving up and aborting (ETIMEDOUT) a connection.
> */
> if (val < 0)
> diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
> new file mode 100644
> index 000000000000..40ee83fc0afe
> --- /dev/null
> +++ b/net/ipv4/tcp_authopt.c
> @@ -0,0 +1,718 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +
> +#include <linux/kernel.h>
> +#include <net/tcp.h>
> +#include <net/tcp_authopt.h>
> +#include <crypto/hash.h>
> +#include <trace/events/tcp.h>
> +
> +/* All current algorithms have a mac length of 12 but crypto API digestsize can be larger */
> +#define TCP_AUTHOPT_MAXMACBUF 20
> +#define TCP_AUTHOPT_MAX_TRAFFIC_KEY_LEN 20
> +
> +struct tcp_authopt_key_info *__tcp_authopt_key_info_lookup(struct sock *sk,
> + struct tcp_authopt_info *info,
> + int key_id)
> +{
> + struct tcp_authopt_key_info *key;
> +
> + hlist_for_each_entry_rcu(key, &info->head, node, lockdep_sock_is_held(sk))
> + if (key->local_id == key_id)
> + return key;
> +
> + return NULL;
> +}
> +
> +struct tcp_authopt_key_info *tcp_authopt_key_info_lookup(struct sock *sk, int key_id)
> +{
> + struct tcp_authopt_info *info;
> + struct tcp_authopt_key_info *key;
> +
> + info = rcu_dereference_check(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk));
> + if (!info)
> + return NULL;
> +
> + hlist_for_each_entry_rcu(key, &info->head, node, lockdep_sock_is_held(sk))
> + if (key->local_id == key_id)
> + return key;
> +
> + return NULL;

The loop and 'return' can be replaced by

return __tcp_authopt_key_info_lookup(sk, info, key_id);

> +}
> +
> +int tcp_set_authopt(struct sock *sk, sockptr_t optval, unsigned int optlen)
> +{
> + struct tcp_sock *tp = tcp_sk(sk);
> + struct tcp_authopt opt;
> + struct tcp_authopt_info *info;
> +
> + if (optlen < sizeof(opt))
> + return -EINVAL;
> +
> + WARN_ON(!lockdep_sock_is_held(sk));
> + if (copy_from_sockptr(&opt, optval, sizeof(opt)))
> + return -EFAULT;
> +
> + info = rcu_dereference_check(tp->authopt_info, lockdep_sock_is_held(sk));
> + if (!info) {
> + info = kmalloc(sizeof(*info), GFP_KERNEL | __GFP_ZERO);
> + if (!info)
> + return -ENOMEM;
> +
> + sk_nocaps_add(sk, NETIF_F_GSO_MASK);
> + INIT_HLIST_HEAD(&info->head);
> + rcu_assign_pointer(tp->authopt_info, info);
> + }

info->flags = opt.flags;

In case we forget to add this in the future.

> + info->local_send_id = opt.local_send_id;
> +
> + return 0;
> +}
> +
> +static void tcp_authopt_key_del(struct sock *sk, struct tcp_authopt_key_info *key)
> +{
> + hlist_del_rcu(&key->node);
> + atomic_sub(sizeof(*key), &sk->sk_omem_alloc);

Should this be done after actually freeing the key?

> + kfree_rcu(key, rcu);
> +}
> +
> +/* free info and keys but don't touch tp->authopt_info */
> +void __tcp_authopt_info_free(struct sock *sk, struct tcp_authopt_info *info)
> +{
> + struct hlist_node *n;
> + struct tcp_authopt_key_info *key;
> +
> + hlist_for_each_entry_safe(key, n, &info->head, node)
> + tcp_authopt_key_del(sk, key);
> + kfree_rcu(info, rcu);
> +}
> +
> +/* free everything and clear tcp_sock.authopt_info to NULL */
> +void tcp_authopt_clear(struct sock *sk)
> +{
> + struct tcp_authopt_info *info;
> +
> + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk));
> + if (info) {
> + __tcp_authopt_info_free(sk, info);
> + tcp_sk(sk)->authopt_info = NULL;
> + }
> +}
> +
> +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;
> + u8 traffic_key_len, maclen;
> +
> + if (optlen < sizeof(opt))
> + return -EINVAL;
> +
> + if (copy_from_sockptr(&opt, optval, sizeof(opt)))
> + return -EFAULT;
> +
> + if (opt.keylen > TCP_AUTHOPT_MAXKEYLEN)
> + return -EINVAL;
> +
> + if (opt.local_id == 0)
> + return -EINVAL;
> +
> + /* must set authopt before setting keys */
> + info = rcu_dereference_protected(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk));
> + if (!info)
> + return -EINVAL;
> +
> + if (opt.flags & TCP_AUTHOPT_KEY_DEL) {
> + key_info = __tcp_authopt_key_info_lookup(sk, info, opt.local_id);
> + if (!key_info)
> + return -ENOENT;
> + tcp_authopt_key_del(sk, key_info);
> + return 0;
> + }
> +
> + /* check the algorithm */
> + if (opt.alg == TCP_AUTHOPT_ALG_HMAC_SHA_1_96) {
> + traffic_key_len = 20;
> + maclen = 12;
> + } else if (opt.alg == TCP_AUTHOPT_ALG_AES_128_CMAC_96) {
> + traffic_key_len = 16;
> + maclen = 12;
> + } else {
> + return -EINVAL;
> + }
> +
> + /* If an old value exists for same local_id it is deleted */
> + key_info = __tcp_authopt_key_info_lookup(sk, info, opt.local_id);
> + if (key_info)
> + tcp_authopt_key_del(sk, key_info);
> + key_info = sock_kmalloc(sk, sizeof(*key_info), GFP_KERNEL | __GFP_ZERO);
> + if (!key_info)
> + return -ENOMEM;
> + key_info->local_id = opt.local_id;
> + key_info->flags = opt.flags & TCP_AUTHOPT_KEY_EXCLUDE_OPTS;
> + key_info->send_id = opt.send_id;
> + key_info->recv_id = opt.recv_id;
> + key_info->alg = opt.alg;
> + key_info->keylen = opt.keylen;
> + memcpy(key_info->key, opt.key, opt.keylen);
> + key_info->maclen = maclen;
> + key_info->traffic_key_len = traffic_key_len;
> + hlist_add_head_rcu(&key_info->node, &info->head);
> +
> + return 0;
> +}

I have looked up to here and will continue tomorrow.

BTW, this patch seems a bit large to me, so splitting it will make it
easier to read.

Kuniyuki