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Date: Tue, 12 Sep 2023 18:47:26 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Dmitry Safonov <dima@...sta.com>
Cc: David Ahern <dsahern@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Jakub Kicinski <kuba@...nel.org>, "David S. Miller" <davem@...emloft.net>, linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>, Ard Biesheuvel <ardb@...nel.org>,
Bob Gilligan <gilligan@...sta.com>, Dan Carpenter <error27@...il.com>,
David Laight <David.Laight@...lab.com>, Dmitry Safonov <0x7f454c46@...il.com>,
Donald Cassidy <dcassidy@...hat.com>, Eric Biggers <ebiggers@...nel.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>, Francesco Ruggeri <fruggeri05@...il.com>,
"Gaillardetz, Dominik" <dgaillar@...na.com>, Herbert Xu <herbert@...dor.apana.org.au>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Ivan Delalande <colona@...sta.com>,
Leonard Crestez <cdleonard@...il.com>, "Nassiri, Mohammad" <mnassiri@...na.com>,
Salam Noureddine <noureddine@...sta.com>, Simon Horman <simon.horman@...igine.com>,
"Tetreault, Francois" <ftetreau@...na.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v11 net-next 06/23] net/tcp: Add TCP-AO sign to outgoing packets
On Mon, Sep 11, 2023 at 11:04 PM Dmitry Safonov <dima@...sta.com> wrote:
>
> Using precalculated traffic keys, sign TCP segments as prescribed by
> RFC5925. Per RFC, TCP header options are included in sign calculation:
> "The TCP header, by default including options, and where the TCP
> checksum and TCP-AO MAC fields are set to zero, all in network-
> byte order." (5.1.3)
>
> tcp_ao_hash_header() has exclude_options parameter to optionally exclude
> TCP header from hash calculation, as described in RFC5925 (9.1), this is
> needed for interaction with middleboxes that may change "some TCP
> options". This is wired up to AO key flags and setsockopt() later.
>
> Similarly to TCP-MD5 hash TCP segment fragments.
>
> From this moment a user can start sending TCP-AO signed segments with
> one of crypto ahash algorithms from supported by Linux kernel. It can
> have a user-specified MAC length, to either save TCP option header space
> or provide higher protection using a longer signature.
> The inbound segments are not yet verified, TCP-AO option is ignored and
> they are accepted.
>
> Co-developed-by: Francesco Ruggeri <fruggeri@...sta.com>
> Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>
> Co-developed-by: Salam Noureddine <noureddine@...sta.com>
> Signed-off-by: Salam Noureddine <noureddine@...sta.com>
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> Acked-by: David Ahern <dsahern@...nel.org>
> ---
> include/net/tcp.h | 4 +
> include/net/tcp_ao.h | 13 ++++
> net/ipv4/tcp_ao.c | 165 ++++++++++++++++++++++++++++++++++++++++++
> net/ipv4/tcp_ipv4.c | 1 +
> net/ipv4/tcp_output.c | 111 +++++++++++++++++++++++++---
> net/ipv6/tcp_ao.c | 28 +++++++
> net/ipv6/tcp_ipv6.c | 2 +
> 7 files changed, 315 insertions(+), 9 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 45df08b5ad28..9d6da2e19dd9 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -185,6 +185,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
> #define TCPOPT_SACK 5 /* SACK Block */
> #define TCPOPT_TIMESTAMP 8 /* Better RTT estimations/PAWS */
> #define TCPOPT_MD5SIG 19 /* MD5 Signature (RFC2385) */
> +#define TCPOPT_AO 29 /* Authentication Option (RFC5925) */
> #define TCPOPT_MPTCP 30 /* Multipath TCP (RFC6824) */
> #define TCPOPT_FASTOPEN 34 /* Fast open (RFC7413) */
> #define TCPOPT_EXP 254 /* Experimental */
> @@ -2158,6 +2159,9 @@ struct tcp_sock_af_ops {
> int (*ao_calc_key_sk)(struct tcp_ao_key *mkt, u8 *key,
> const struct sock *sk,
> __be32 sisn, __be32 disn, bool send);
> + int (*calc_ao_hash)(char *location, struct tcp_ao_key *ao,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne);
> #endif
> };
>
> diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
> index 7e0ce45d9934..cd85d292f78e 100644
> --- a/include/net/tcp_ao.h
> +++ b/include/net/tcp_ao.h
> @@ -111,6 +111,10 @@ struct tcp6_ao_context {
>
> struct tcp_sigpool;
>
> +int tcp_ao_hash_skb(unsigned short int family,
> + char *ao_hash, struct tcp_ao_key *key,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne);
> int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
> sockptr_t optval, int optlen);
> int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
> @@ -126,12 +130,21 @@ struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
> int tcp_v4_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
> const struct sock *sk,
> __be32 sisn, __be32 disn, bool send);
> +int tcp_v4_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne);
> /* ipv6 specific functions */
> +int tcp_v6_ao_hash_pseudoheader(struct tcp_sigpool *hp,
> + const struct in6_addr *daddr,
> + const struct in6_addr *saddr, int nbytes);
> int tcp_v6_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
> const struct sock *sk, __be32 sisn,
> __be32 disn, bool send);
> struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
> struct sock *addr_sk, int sndid, int rcvid);
> +int tcp_v6_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne);
> int tcp_v6_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen);
> void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);
> void tcp_ao_connect_init(struct sock *sk);
> diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
> index fc7a6aa1936e..d10daee79fe6 100644
> --- a/net/ipv4/tcp_ao.c
> +++ b/net/ipv4/tcp_ao.c
> @@ -262,6 +262,171 @@ static int tcp_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
> return -EOPNOTSUPP;
> }
>
> +static int tcp_v4_ao_hash_pseudoheader(struct tcp_sigpool *hp,
> + __be32 daddr, __be32 saddr,
> + int nbytes)
> +{
> + struct tcp4_pseudohdr *bp;
> + struct scatterlist sg;
> +
> + bp = hp->scratch;
> + bp->saddr = saddr;
> + bp->daddr = daddr;
> + bp->pad = 0;
> + bp->protocol = IPPROTO_TCP;
> + bp->len = cpu_to_be16(nbytes);
> +
> + sg_init_one(&sg, bp, sizeof(*bp));
> + ahash_request_set_crypt(hp->req, &sg, NULL, sizeof(*bp));
> + return crypto_ahash_update(hp->req);
> +}
> +
> +static int tcp_ao_hash_pseudoheader(unsigned short int family,
> + const struct sock *sk,
> + const struct sk_buff *skb,
> + struct tcp_sigpool *hp, int nbytes)
> +{
> + const struct tcphdr *th = tcp_hdr(skb);
> +
> + /* TODO: Can we rely on checksum being zero to mean outbound pkt? */
> + if (!th->check) {
> + if (family == AF_INET)
> + return tcp_v4_ao_hash_pseudoheader(hp, sk->sk_daddr,
> + sk->sk_rcv_saddr, skb->len);
> +#if IS_ENABLED(CONFIG_IPV6)
> + else if (family == AF_INET6)
> + return tcp_v6_ao_hash_pseudoheader(hp, &sk->sk_v6_daddr,
> + &sk->sk_v6_rcv_saddr, skb->len);
> +#endif
> + else
> + return -EAFNOSUPPORT;
> + }
> +
> + if (family == AF_INET) {
> + const struct iphdr *iph = ip_hdr(skb);
> +
> + return tcp_v4_ao_hash_pseudoheader(hp, iph->daddr,
> + iph->saddr, skb->len);
> +#if IS_ENABLED(CONFIG_IPV6)
> + } else if (family == AF_INET6) {
> + const struct ipv6hdr *iph = ipv6_hdr(skb);
> +
> + return tcp_v6_ao_hash_pseudoheader(hp, &iph->daddr,
> + &iph->saddr, skb->len);
> +#endif
> + }
> + return -EAFNOSUPPORT;
> +}
> +
> +/* tcp_ao_hash_sne(struct tcp_sigpool *hp)
> + * @hp - used for hashing
> + * @sne - sne value
> + */
> +static int tcp_ao_hash_sne(struct tcp_sigpool *hp, u32 sne)
> +{
> + struct scatterlist sg;
> + __be32 *bp;
> +
> + bp = (__be32 *)hp->scratch;
> + *bp = htonl(sne);
> +
> + sg_init_one(&sg, bp, sizeof(*bp));
> + ahash_request_set_crypt(hp->req, &sg, NULL, sizeof(*bp));
> + return crypto_ahash_update(hp->req);
> +}
> +
> +static int tcp_ao_hash_header(struct tcp_sigpool *hp,
> + const struct tcphdr *th,
> + bool exclude_options, u8 *hash,
> + int hash_offset, int hash_len)
> +{
> + int err, len = th->doff << 2;
> + struct scatterlist sg;
> + u8 *hdr = hp->scratch;
> +
> + /* We are not allowed to change tcphdr, make a local copy */
> + if (exclude_options) {
> + len = sizeof(*th) + sizeof(struct tcp_ao_hdr) + hash_len;
> + memcpy(hdr, th, sizeof(*th));
> + memcpy(hdr + sizeof(*th),
> + (u8 *)th + hash_offset - sizeof(struct tcp_ao_hdr),
> + sizeof(struct tcp_ao_hdr));
> + memset(hdr + sizeof(*th) + sizeof(struct tcp_ao_hdr),
> + 0, hash_len);
> + ((struct tcphdr *)hdr)->check = 0;
> + } else {
> + len = th->doff << 2;
> + memcpy(hdr, th, len);
> + /* zero out tcp-ao hash */
> + ((struct tcphdr *)hdr)->check = 0;
> + memset(hdr + hash_offset, 0, hash_len);
> + }
> +
> + sg_init_one(&sg, hdr, len);
> + ahash_request_set_crypt(hp->req, &sg, NULL, len);
> + err = crypto_ahash_update(hp->req);
> + WARN_ON_ONCE(err != 0);
> + return err;
> +}
> +
> +int tcp_ao_hash_skb(unsigned short int family,
> + char *ao_hash, struct tcp_ao_key *key,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne)
> +{
> + const struct tcphdr *th = tcp_hdr(skb);
> + int tkey_len = tcp_ao_digest_size(key);
> + struct tcp_sigpool hp;
> + void *hash_buf = NULL;
> +
> + hash_buf = kmalloc(tkey_len, GFP_ATOMIC);
> + if (!hash_buf)
> + goto clear_hash_noput;
> +
> + if (tcp_sigpool_start(key->tcp_sigpool_id, &hp))
> + goto clear_hash_noput;
> +
> + if (crypto_ahash_setkey(crypto_ahash_reqtfm(hp.req), tkey, tkey_len))
> + goto clear_hash;
> +
> + /* For now use sha1 by default. Depends on alg in tcp_ao_key */
> + if (crypto_ahash_init(hp.req))
> + goto clear_hash;
> +
> + if (tcp_ao_hash_sne(&hp, sne))
> + goto clear_hash;
> + if (tcp_ao_hash_pseudoheader(family, sk, skb, &hp, skb->len))
> + goto clear_hash;
> + if (tcp_ao_hash_header(&hp, th, false,
> + ao_hash, hash_offset, tcp_ao_maclen(key)))
> + goto clear_hash;
> + if (tcp_sigpool_hash_skb_data(&hp, skb, th->doff << 2))
> + goto clear_hash;
> + ahash_request_set_crypt(hp.req, NULL, hash_buf, 0);
> + if (crypto_ahash_final(hp.req))
> + goto clear_hash;
> +
> + memcpy(ao_hash, hash_buf, tcp_ao_maclen(key));
> + tcp_sigpool_end(&hp);
> + kfree(hash_buf);
> + return 0;
> +
> +clear_hash:
> + tcp_sigpool_end(&hp);
> +clear_hash_noput:
> + memset(ao_hash, 0, tcp_ao_maclen(key));
> + kfree(hash_buf);
> + return 1;
> +}
> +
> +int tcp_v4_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key,
> + const struct sock *sk, const struct sk_buff *skb,
> + const u8 *tkey, int hash_offset, u32 sne)
> +{
> + return tcp_ao_hash_skb(AF_INET, ao_hash, key, sk, skb,
> + tkey, hash_offset, sne);
> +}
> +
> struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
> int sndid, int rcvid)
> {
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index d63970b3d375..ed26676735a5 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -2284,6 +2284,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv4_specific = {
> #endif
> #ifdef CONFIG_TCP_AO
> .ao_lookup = tcp_v4_ao_lookup,
> + .calc_ao_hash = tcp_v4_ao_hash_skb,
> .ao_parse = tcp_v4_parse_ao,
> .ao_calc_key_sk = tcp_v4_ao_calc_key_sk,
> #endif
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 705eeb623269..01424b82845a 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -423,6 +423,7 @@ static inline bool tcp_urg_mode(const struct tcp_sock *tp)
> #define OPTION_FAST_OPEN_COOKIE BIT(8)
> #define OPTION_SMC BIT(9)
> #define OPTION_MPTCP BIT(10)
> +#define OPTION_AO BIT(11)
>
> static void smc_options_write(__be32 *ptr, u16 *options)
> {
> @@ -615,7 +616,8 @@ static void bpf_skops_write_hdr_opt(struct sock *sk, struct sk_buff *skb,
> * (but it may well be that other scenarios fail similarly).
> */
> static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
> - struct tcp_out_options *opts)
> + struct tcp_out_options *opts,
> + struct tcp_ao_key *ao_key)
> {
> __be32 *ptr = (__be32 *)(th + 1);
> u16 options = opts->options; /* mungable copy */
> @@ -627,7 +629,33 @@ static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
> opts->hash_location = (__u8 *)ptr;
> ptr += 4;
> }
> +#ifdef CONFIG_TCP_AO
> + if (unlikely(OPTION_AO & options)) {
> + struct tcp_ao_key *rnext_key;
> + struct tcp_ao_info *ao_info;
> + u8 maclen;
>
> + if (WARN_ON_ONCE(!ao_key))
> + goto out_ao;
> + ao_info = rcu_dereference_check(tp->ao_info,
> + lockdep_sock_is_held(&tp->inet_conn.icsk_inet.sk));
> + rnext_key = READ_ONCE(ao_info->rnext_key);
> + if (WARN_ON_ONCE(!rnext_key))
> + goto out_ao;
> + maclen = tcp_ao_maclen(ao_key);
> + *ptr++ = htonl((TCPOPT_AO << 24) |
> + (tcp_ao_len(ao_key) << 16) |
> + (ao_key->sndid << 8) |
> + (rnext_key->rcvid));
> + opts->hash_location = (__u8 *)ptr;
> + ptr += maclen / sizeof(*ptr);
> + if (unlikely(maclen % sizeof(*ptr))) {
> + memset(ptr, TCPOPT_NOP, sizeof(*ptr));
> + ptr++;
> + }
> + }
> +out_ao:
> +#endif
> if (unlikely(opts->mss)) {
> *ptr++ = htonl((TCPOPT_MSS << 24) |
> (TCPOLEN_MSS << 16) |
> @@ -768,7 +796,8 @@ static void mptcp_set_option_cond(const struct request_sock *req,
> */
> static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
> struct tcp_out_options *opts,
> - struct tcp_md5sig_key **md5)
> + struct tcp_md5sig_key **md5,
> + struct tcp_ao_key *ao_key)
> {
> struct tcp_sock *tp = tcp_sk(sk);
> unsigned int remaining = MAX_TCP_OPTION_SPACE;
> @@ -785,6 +814,12 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
> }
> }
> #endif
> +#ifdef CONFIG_TCP_AO
> + if (ao_key) {
> + opts->options |= OPTION_AO;
> + remaining -= tcp_ao_len(ao_key);
> + }
> +#endif
>
> /* We always get an MSS option. The option bytes which will be seen in
> * normal data packets should timestamps be used, must be in the MSS
> @@ -922,7 +957,8 @@ static unsigned int tcp_synack_options(const struct sock *sk,
> */
> static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb,
> struct tcp_out_options *opts,
> - struct tcp_md5sig_key **md5)
> + struct tcp_md5sig_key **md5,
> + struct tcp_ao_key *ao_key)
> {
> struct tcp_sock *tp = tcp_sk(sk);
> unsigned int size = 0;
> @@ -941,6 +977,12 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
> }
> }
> #endif
> +#ifdef CONFIG_TCP_AO
> + if (ao_key) {
> + opts->options |= OPTION_AO;
> + size += tcp_ao_len(ao_key);
> + }
> +#endif
>
> if (likely(tp->rx_opt.tstamp_ok)) {
> opts->options |= OPTION_TS;
> @@ -1245,6 +1287,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
> int clone_it, gfp_t gfp_mask, u32 rcv_nxt)
> {
> const struct inet_connection_sock *icsk = inet_csk(sk);
> + struct tcp_ao_key *ao_key = NULL;
> struct inet_sock *inet;
> struct tcp_sock *tp;
> struct tcp_skb_cb *tcb;
> @@ -1252,6 +1295,9 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
> unsigned int tcp_options_size, tcp_header_size;
> struct sk_buff *oskb = NULL;
> struct tcp_md5sig_key *md5;
> +#ifdef CONFIG_TCP_AO
> + struct tcp_ao_info *ao;
> +#endif
> struct tcphdr *th;
> u64 prior_wstamp;
> int err;
> @@ -1283,11 +1329,17 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
> tcb = TCP_SKB_CB(skb);
> memset(&opts, 0, sizeof(opts));
>
> +#ifdef CONFIG_TCP_AO
> + ao = rcu_dereference_protected(tcp_sk(sk)->ao_info,
> + lockdep_sock_is_held(sk));
> + if (ao)
> + ao_key = READ_ONCE(ao->current_key);
> +#endif
> if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
> - tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
> + tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5, ao_key);
> } else {
> tcp_options_size = tcp_established_options(sk, skb, &opts,
> - &md5);
> + &md5, ao_key);
> /* Force a PSH flag on all (GSO) packets to expedite GRO flush
> * at receiver : This slightly improve GRO performance.
> * Note that we do not force the PSH flag for non GSO packets,
> @@ -1368,7 +1420,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
> th->window = htons(min(tp->rcv_wnd, 65535U));
> }
>
> - tcp_options_write(th, tp, &opts);
> + tcp_options_write(th, tp, &opts, ao_key);
>
> #ifdef CONFIG_TCP_MD5SIG
> /* Calculate the MD5 hash, as we have all we need now */
> @@ -1378,6 +1430,34 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
> md5, sk, skb);
> }
> #endif
> +#ifdef CONFIG_TCP_AO
> + if (ao) {
> + u8 *traffic_key;
> + void *tkey_buf = NULL;
> + __be32 disn;
> +
> + sk_gso_disable(sk);
Why is this needed here in a fast path ? This should happen once.
It seems you copied MD5 old logic, I think we should do better.
> + if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) {
> + if (tcb->tcp_flags & TCPHDR_ACK)
> + disn = ao->risn;
> + else
> + disn = 0;
> +
> + tkey_buf = kmalloc(tcp_ao_digest_size(ao_key), GFP_ATOMIC);
> + if (!tkey_buf)
> + return -ENOMEM;
This leaks an skb.
> + traffic_key = tkey_buf;
> + tp->af_specific->ao_calc_key_sk(ao_key, traffic_key,
> + sk, ao->lisn, disn, true);
> + } else {
> + traffic_key = snd_other_key(ao_key);
> + }
> + tp->af_specific->calc_ao_hash(opts.hash_location, ao_key, sk, skb,
> + traffic_key,
> + opts.hash_location - (u8 *)th, 0);
> + kfree(tkey_buf);
> + }
> +#endif
>
> /* BPF prog is the last one writing header option */
> bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
> @@ -1825,10 +1905,14 @@ unsigned int tcp_current_mss(struct sock *sk)
> {
> const struct tcp_sock *tp = tcp_sk(sk);
> const struct dst_entry *dst = __sk_dst_get(sk);
> + struct tcp_ao_key *ao_key = NULL;
> u32 mss_now;
> unsigned int header_len;
> struct tcp_out_options opts;
> struct tcp_md5sig_key *md5;
> +#ifdef CONFIG_TCP_AO
> + struct tcp_ao_info *ao_info;
> +#endif
>
> mss_now = tp->mss_cache;
>
> @@ -1837,8 +1921,17 @@ unsigned int tcp_current_mss(struct sock *sk)
> if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
> mss_now = tcp_sync_mss(sk, mtu);
> }
> -
> - header_len = tcp_established_options(sk, NULL, &opts, &md5) +
> +#ifdef CONFIG_TCP_AO
> + ao_info = rcu_dereference_check(tp->ao_info, lockdep_sock_is_held(sk));
> + if (ao_info)
> + /* TODO: verify if we can access current_key or we need to pass
> + * it from every caller of tcp_current_mss instead. The reason
> + * is that the current_key pointer can change asynchronously
> + * from the rx path.
> + */
> + ao_key = READ_ONCE(ao_info->current_key);
> +#endif
> + header_len = tcp_established_options(sk, NULL, &opts, &md5, ao_key) +
> sizeof(struct tcphdr);
Adding yet another argument in TCP fast path routines is very unfortunate...
Could we merge md5/ao_key, and have a field giving the type ?
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