Subject: [07/12] secure_seq: use the 64 bits of the siphash for port offset calculation

From: Willy Tarreau <[email-masked]>
Date: Mon, 2 May 2022 10:46:08 +0200

commit b2d057560b8107c633b39aabe517ff9d93f285e3 upstream.

SipHash replaced MD5 in secure_ipv{4,6}_port_ephemeral() via commit
7cd23e5300c1 ("secure_seq: use SipHash in place of MD5"), but the output
remained truncated to 32-bit only. In order to exploit more bits from the
hash, let's make the functions return the full 64-bit of siphash_3u32().
We also make sure the port offset calculation in __inet_hash_connect()
remains done on 32-bit to avoid the need for div_u64_rem() and an extra
cost on 32-bit systems.

Cc: Jason A. Donenfeld <[email-masked]>
Cc: Moshe Kol <[email-masked]>
Cc: Yossi Gilad <[email-masked]>
Cc: Amit Klein <[email-masked]>
Reviewed-by: Eric Dumazet <[email-masked]>
Signed-off-by: Willy Tarreau <[email-masked]>
Signed-off-by: Jakub Kicinski <[email-masked]>
Signed-off-by: Ben Hutchings <[email-masked]>
---
 include/net/inet_hashtables.h |  2 +-
 include/net/secure_seq.h      |  4 ++--
 net/core/secure_seq.c         |  4 ++--
 net/ipv4/inet_hashtables.c    | 10 ++++++----
 net/ipv6/inet6_hashtables.c   |  4 ++--
 5 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index fc445e7ccadf..c3cf2021bb3b 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -382,7 +382,7 @@ static inline void sk_rcv_saddr_set(struct sock *sk, __be32 addr)
 }
 
 int __inet_hash_connect(struct inet_timewait_death_row *death_row,
-			struct sock *sk, u32 port_offset,
+			struct sock *sk, u64 port_offset,
 			int (*check_established)(struct inet_timewait_death_row *,
 						 struct sock *, __u16,
 						 struct inet_timewait_sock **));
diff --git a/include/net/secure_seq.h b/include/net/secure_seq.h
index 3f36d45b714a..542a80c05107 100644
--- a/include/net/secure_seq.h
+++ b/include/net/secure_seq.h
@@ -3,8 +3,8 @@
 
 #include <linux/types.h>
 
-u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
-u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
+u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport);
+u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 			       __be16 dport);
 __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
 				 __be16 sport, __be16 dport);
diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index fd3ce461fbe6..ed05b8277aa4 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -62,7 +62,7 @@ __u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
 }
 EXPORT_SYMBOL(secure_tcpv6_sequence_number);
 
-u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
+u64 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 			       __be16 dport)
 {
 	u32 secret[MD5_MESSAGE_BYTES / 4];
@@ -102,7 +102,7 @@ __u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
 	return seq_scale(hash[0]);
 }
 
-u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
+u64 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
 {
 	u32 hash[MD5_DIGEST_WORDS];
 
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 6dc2afaa330f..025e87ed97a2 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -382,7 +382,7 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
 	return -EADDRNOTAVAIL;
 }
 
-static u32 inet_sk_port_offset(const struct sock *sk)
+static u64 inet_sk_port_offset(const struct sock *sk)
 {
 	const struct inet_sock *inet = inet_sk(sk);
 
@@ -549,7 +549,7 @@ EXPORT_SYMBOL_GPL(inet_unhash);
 static u32 table_perturb[1 << INET_TABLE_PERTURB_SHIFT];
 
 int __inet_hash_connect(struct inet_timewait_death_row *death_row,
-		struct sock *sk, u32 port_offset,
+		struct sock *sk, u64 port_offset,
 		int (*check_established)(struct inet_timewait_death_row *,
 			struct sock *, __u16, struct inet_timewait_sock **))
 {
@@ -589,7 +589,9 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 	net_get_random_once(table_perturb, sizeof(table_perturb));
 	index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT);
 
-	offset = (READ_ONCE(table_perturb[index]) + port_offset) % remaining;
+	offset = READ_ONCE(table_perturb[index]) + port_offset;
+	offset %= remaining;
+
 	/* In first pass we try ports of @low parity.
 	 * inet_csk_get_port() does the opposite choice.
 	 */
@@ -670,7 +672,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 int inet_hash_connect(struct inet_timewait_death_row *death_row,
 		      struct sock *sk)
 {
-	u32 port_offset = 0;
+	u64 port_offset = 0;
 
 	if (!inet_sk(sk)->inet_num)
 		port_offset = inet_sk_port_offset(sk);
diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index d47cab6d7c6d..8223ac61a9fd 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -242,7 +242,7 @@ static int __inet6_check_established(struct inet_timewait_death_row *death_row,
 	return -EADDRNOTAVAIL;
 }
 
-static u32 inet6_sk_port_offset(const struct sock *sk)
+static u64 inet6_sk_port_offset(const struct sock *sk)
 {
 	const struct inet_sock *inet = inet_sk(sk);
 
@@ -254,7 +254,7 @@ static u32 inet6_sk_port_offset(const struct sock *sk)
 int inet6_hash_connect(struct inet_timewait_death_row *death_row,
 		       struct sock *sk)
 {
-	u32 port_offset = 0;
+	u64 port_offset = 0;
 
 	if (!inet_sk(sk)->inet_num)
 		port_offset = inet6_sk_port_offset(sk);