[PATCH 07/31] tcp: Add TCP-AO config and structures

[Dmitry Safonov <dima@arista.com>]

Introduce new kernel config option and common structures as well as
helpers to be used by TCP-AO code.

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/linux/tcp.h      |  3 ++
 include/net/tcp.h        |  8 +---
 include/net/tcp_ao.h     | 90 ++++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/tcp.h |  2 +
 net/ipv4/Kconfig         | 13 ++++++
 5 files changed, 110 insertions(+), 6 deletions(-)
 create mode 100644 include/net/tcp_ao.h

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a9fbe22732c3..c8a8aaaf725b 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -435,6 +435,9 @@ struct tcp_sock {
 /* TCP MD5 Signature Option information */
 	struct tcp_md5sig_info	__rcu *md5sig_info;
 #endif
+#ifdef CONFIG_TCP_AO
+	struct tcp_ao_info	__rcu *ao_info;
+#endif
 
 /* TCP fastopen related information */
 	struct tcp_fastopen_request *fastopen_req;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 75bb817928c1..b4b009094bf6 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -37,6 +37,7 @@
 #include <net/snmp.h>
 #include <net/ip.h>
 #include <net/tcp_states.h>
+#include <net/tcp_ao.h>
 #include <net/inet_ecn.h>
 #include <net/dst.h>
 #include <net/mptcp.h>
@@ -1605,12 +1606,7 @@ static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
 	tp->retransmit_skb_hint = NULL;
 }
 
-union tcp_md5_addr {
-	struct in_addr  a4;
-#if IS_ENABLED(CONFIG_IPV6)
-	struct in6_addr	a6;
-#endif
-};
+#define tcp_md5_addr tcp_ao_addr
 
 /* - key database */
 struct tcp_md5sig_key {
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
new file mode 100644
index 000000000000..39b3fc31e5a1
--- /dev/null
+++ b/include/net/tcp_ao.h
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef _TCP_AO_H
+#define _TCP_AO_H
+
+#define TCP_AO_MAX_HASH_SIZE	64
+#define TCP_AO_KEY_ALIGN	1
+#define __tcp_ao_key_align __aligned(TCP_AO_KEY_ALIGN)
+
+union tcp_ao_addr {
+	struct in_addr  a4;
+#if IS_ENABLED(CONFIG_IPV6)
+	struct in6_addr	a6;
+#endif
+};
+
+struct tcp_ao_hdr {
+	u8	kind;
+	u8	length;
+	u8	keyid;
+	u8	rnext_keyid;
+};
+
+struct tcp_ao_key {
+	struct hlist_node	node;
+	union tcp_ao_addr	addr;
+	u8			key[TCP_AO_MAXKEYLEN] __tcp_ao_key_align;
+	unsigned int		crypto_pool_id;
+	u16			port;
+	u8			prefixlen;
+	u8			family;
+	u8			keylen;
+	u8			keyflags;
+	u8			sndid;
+	u8			rcvid;
+	u8			maclen;
+	u8			digest_size;
+	struct rcu_head		rcu;
+	u8			traffic_keys[];
+};
+
+static inline u8 *rcv_other_key(struct tcp_ao_key *key)
+{
+	return key->traffic_keys;
+}
+
+static inline u8 *snd_other_key(struct tcp_ao_key *key)
+{
+	return key->traffic_keys + key->digest_size;
+}
+
+static inline int tcp_ao_maclen(const struct tcp_ao_key *key)
+{
+	return key->maclen;
+}
+
+static inline int tcp_ao_sizeof_key(const struct tcp_ao_key *key)
+{
+	return sizeof(struct tcp_ao_key) + (TCP_AO_MAX_HASH_SIZE << 1);
+}
+
+static inline int tcp_ao_len(const struct tcp_ao_key *key)
+{
+	return tcp_ao_maclen(key) + sizeof(struct tcp_ao_hdr);
+}
+
+static inline unsigned int tcp_ao_digest_size(struct tcp_ao_key *key)
+{
+	return key->digest_size;
+}
+
+struct tcp_ao_info {
+	struct hlist_head	head;
+	struct rcu_head		rcu;
+	/* current_key and rnext_key aren't maintained on listen sockets.
+	 * Their purpose is to cache keys on established connections,
+	 * saving needless lookups. Never dereference any of them from
+	 * listen sockets.
+	 */
+	struct tcp_ao_key	*volatile current_key;
+	struct tcp_ao_key	*rnext_key;
+	u8			ao_flags;
+	__be32			lisn;
+	__be32			risn;
+	u32			snd_sne;
+	u32			snd_sne_seq;
+	u32			rcv_sne;
+	u32			rcv_sne_seq;
+};
+
+#endif /* _TCP_AO_H */
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 8fc09e8638b3..849bbf2d3c38 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -342,6 +342,8 @@ struct tcp_diag_md5sig {
 	__u8	tcpm_key[TCP_MD5SIG_MAXKEYLEN];
 };
 
+#define TCP_AO_MAXKEYLEN	80
+
 /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */
 
 #define TCP_RECEIVE_ZEROCOPY_FLAG_TLB_CLEAN_HINT 0x1
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index c341864e4398..89bd0e9d97fe 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -731,6 +731,19 @@ config DEFAULT_TCP_CONG
 	default "bbr" if DEFAULT_BBR
 	default "cubic"
 
+config TCP_AO
+	bool "TCP: Authentication Option (rfc5925)"
+	select CRYPTO
+	select CRYPTO_POOL
+	select TCP_MD5SIG
+	depends on 64BIT # seq-number extension needs WRITE_ONCE(u64)
+	default y
+	help
+	  TCP-AO specifies the use of stronger Message Authentication Codes (MACs),
+	  protects against replays for long-lived TCP connections, and
+	  provides more details on the association of security with TCP
+	  connections than TCP MD5 (See RFC5925)
+
 config TCP_MD5SIG
 	bool "TCP: MD5 Signature Option support (RFC2385)"
 	select CRYPTO_POOL
-- 
2.37.2