[PATCH v3 22/36] net/tcp: Add option for TCP-AO to (not) hash header

Dmitry Safonov
2022-10-27T20:51:11Z

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 e5b4e9f1e83e..90b864d4ee7d 100644
--- a/net/ipv4/tcp_ao.c
+++ b/net/ipv4/tcp_ao.c
@@ -604,7 +604,8 @@ int tcp_ao_hash_hdr(unsigned short int family, char *ao_hash,
WARN_ON_ONCE(1);
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);
@@ -646,7 +647,8 @@ 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))
@@ -1497,7 +1499,7 @@ static inline bool tcp_ao_mkt_overlap_v6(struct tcp_ao *cmd,
}
#endif

-#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 \
--
2.38.1