[PATCH 22/31] net/tcp: Add option for TCP-AO to (not) hash header

[Dmitry Safonov <dima@arista.com>]

Provide setsockopt() key flag that makes TCP-AO exclude hashing TCP
header for peers that match the key. This is needed for interraction
with middleboxes that may change TCP options, see RFC5925 (9.2).

Co-developed-by: Francesco Ruggeri <fruggeri@arista.com>
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Co-developed-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Salam Noureddine <noureddine@arista.com>
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 include/uapi/linux/tcp.h | 2 ++
 net/ipv4/tcp_ao.c        | 8 +++++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 508bedbc6ad8..b60933ee2a27 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -347,6 +347,8 @@ struct tcp_diag_md5sig {
 
 #define TCP_AO_MAXKEYLEN	80
 
+#define TCP_AO_KEYF_EXCLUDE_OPT	(1 << 0)
+
 #define TCP_AO_CMDF_CURR	(1 << 0)	/* Only checks field sndid */
 #define TCP_AO_CMDF_NEXT	(1 << 1)	/* Only checks field rcvid */
 #define TCP_AO_CMDF_ACCEPT_ICMP	(1 << 2)	/* Accept incoming ICMPs */
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
index 858295393643..6e18a8cdee90 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -586,7 +586,8 @@ int tcp_ao_hash_hdr(unsigned short int family, char *ao_hash,
 						&saddr->a6, th->doff * 4))
 			goto clear_hash;
 	}
-	if (tcp_ao_hash_header(&hp, th, false,
+	if (tcp_ao_hash_header(&hp, th,
+			       !!(key->keyflags & TCP_AO_KEYF_EXCLUDE_OPT),
 			       ao_hash, hash_offset, tcp_ao_maclen(key)))
 		goto clear_hash;
 	ahash_request_set_crypt(hp.req, NULL, ao_hash, 0);
@@ -628,7 +629,8 @@ int tcp_ao_hash_skb(unsigned short int family,
 		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,
+	if (tcp_ao_hash_header(&hp, th,
+			       !!(key->keyflags & TCP_AO_KEYF_EXCLUDE_OPT),
 			       ao_hash, hash_offset, tcp_ao_maclen(key)))
 		goto clear_hash;
 	if (tcp_ao_hash_skb_data(&hp, skb, th->doff << 2))
@@ -1416,7 +1418,7 @@ static bool tcp_ao_mkt_overlap_v6(struct tcp_ao *cmd,
 	return false;
 }
 
-#define TCP_AO_KEYF_ALL		(0)
+#define TCP_AO_KEYF_ALL		(TCP_AO_KEYF_EXCLUDE_OPT)
 #define TCP_AO_CMDF_ADDMOD_VALID					\
 	(TCP_AO_CMDF_CURR | TCP_AO_CMDF_NEXT | TCP_AO_CMDF_ACCEPT_ICMP)
 #define TCP_AO_CMDF_DEL_VALID						\
-- 
2.37.2