[PATCH v5 2/5] net/tcp: Consistently align TCP-AO option in the header

Dmitry Safonov
2023-12-04T19:01:09Z

Currently functions that pre-calculate TCP header options length use
unaligned TCP-AO header + MAC-length for skb reservation.
And the functions that actually write TCP-AO options into skb do align
the header. Nothing good can come out of this for ((maclen % 4) != 0).

Provide tcp_ao_len_aligned() helper and use it everywhere for TCP
header options space calculations.

Fixes: 1e03d32bea8e ("net/tcp: Add TCP-AO sign to outgoing packets")
Signed-off-by: Dmitry Safonov <dima@arista.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
include/net/tcp_ao.h | 6 ++++++
net/ipv4/tcp_ao.c | 4 ++--
net/ipv4/tcp_ipv4.c | 4 ++--
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv4/tcp_output.c | 6 +++---
net/ipv6/tcp_ipv6.c | 2 +-
6 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
index b56be10838f0..647781080613 100644
--- a/include/net/tcp_ao.h
+++ b/include/net/tcp_ao.h
@@ -62,11 +62,17 @@ static inline int tcp_ao_maclen(const struct tcp_ao_key *key)
return key->maclen;
}

+/* Use tcp_ao_len_aligned() for TCP header calculations */
static inline int tcp_ao_len(const struct tcp_ao_key *key)
{
return tcp_ao_maclen(key) + sizeof(struct tcp_ao_hdr);
}

+static inline int tcp_ao_len_aligned(const struct tcp_ao_key *key)
+{
+ return round_up(tcp_ao_len(key), 4);
+}
+
static inline unsigned int tcp_ao_digest_size(struct tcp_ao_key *key)
{
return key->digest_size;
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 7696417d0640..c8be1d526eac 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -1100,7 +1100,7 @@ void tcp_ao_connect_init(struct sock *sk)
ao_info->current_key = key;
if (!ao_info->rnext_key)
ao_info->rnext_key = key;
- tp->tcp_header_len += tcp_ao_len(key);
+ tp->tcp_header_len += tcp_ao_len_aligned(key);

ao_info->lisn = htonl(tp->write_seq);
ao_info->snd_sne = 0;
@@ -1346,7 +1346,7 @@ static int tcp_ao_parse_crypto(struct tcp_ao_add *cmd, struct tcp_ao_key *key)
syn_tcp_option_space -= TCPOLEN_MSS_ALIGNED;
syn_tcp_option_space -= TCPOLEN_TSTAMP_ALIGNED;
syn_tcp_option_space -= TCPOLEN_WSCALE_ALIGNED;
- if (tcp_ao_len(key) > syn_tcp_option_space) {
+ if (tcp_ao_len_aligned(key) > syn_tcp_option_space) {
err = -EMSGSIZE;
goto err_kfree;
}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5f693bbd578d..0c50c5a32b84 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -690,7 +690,7 @@ static bool tcp_v4_ao_sign_reset(const struct sock *sk, struct sk_buff *skb,

reply_options[0] = htonl((TCPOPT_AO << 24) | (tcp_ao_len(key) << 16) |
(aoh->rnext_keyid << 8) | keyid);
- arg->iov[0].iov_len += round_up(tcp_ao_len(key), 4);
+ arg->iov[0].iov_len += tcp_ao_len_aligned(key);
reply->doff = arg->iov[0].iov_len / 4;

if (tcp_ao_hash_hdr(AF_INET, (char *)&reply_options[1],
@@ -978,7 +978,7 @@ static void tcp_v4_send_ack(const struct sock *sk,
(tcp_ao_len(key->ao_key) << 16) |
(key->ao_key->sndid << 8) |
key->rcv_next);
- arg.iov[0].iov_len += round_up(tcp_ao_len(key->ao_key), 4);
+ arg.iov[0].iov_len += tcp_ao_len_aligned(key->ao_key);
rep.th.doff = arg.iov[0].iov_len / 4;

tcp_ao_hash_hdr(AF_INET, (char *)&rep.opt[offset],
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index a9807eeb311c..9e85f2a0bddd 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -615,7 +615,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
ao_key = treq->af_specific->ao_lookup(sk, req,
tcp_rsk(req)->ao_keyid, -1);
if (ao_key)
- newtp->tcp_header_len += tcp_ao_len(ao_key);
+ newtp->tcp_header_len += tcp_ao_len_aligned(ao_key);
#endif
if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len)
newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index eb13a55d660c..93eef1dbbc55 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -825,7 +825,7 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb,
timestamps = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_timestamps);
if (tcp_key_is_ao(key)) {
opts->options |= OPTION_AO;
- remaining -= tcp_ao_len(key->ao_key);
+ remaining -= tcp_ao_len_aligned(key->ao_key);
}
}

@@ -915,7 +915,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
ireq->tstamp_ok &= !ireq->sack_ok;
} else if (tcp_key_is_ao(key)) {
opts->options |= OPTION_AO;
- remaining -= tcp_ao_len(key->ao_key);
+ remaining -= tcp_ao_len_aligned(key->ao_key);
ireq->tstamp_ok &= !ireq->sack_ok;
}

@@ -982,7 +982,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb
size += TCPOLEN_MD5SIG_ALIGNED;
} else if (tcp_key_is_ao(key)) {
opts->options |= OPTION_AO;
- size += tcp_ao_len(key->ao_key);
+ size += tcp_ao_len_aligned(key->ao_key);
}

if (likely(tp->rx_opt.tstamp_ok)) {
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 937a02c2e534..8c6623496dd7 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -881,7 +881,7 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
if (tcp_key_is_md5(key))
tot_len += TCPOLEN_MD5SIG_ALIGNED;
if (tcp_key_is_ao(key))
- tot_len += tcp_ao_len(key->ao_key);
+ tot_len += tcp_ao_len_aligned(key->ao_key);

#ifdef CONFIG_MPTCP
if (rst && !tcp_key_is_md5(key)) {
--
2.43.0