netdev - [PATCH 2/2] net: fastopen: use endianness agnostic representation of the cookie

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Date:   Tue, 18 Jun 2019 11:32:07 +0200
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     netdev@...r.kernel.org
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Eric Biggers <ebiggers@...nel.org>,
        linux-crypto@...r.kernel.org, herbert@...dor.apana.org.au,
        edumazet@...gle.com, davem@...emloft.net, kuznet@....inr.ac.ru,
        yoshfuji@...ux-ipv6.org, jbaron@...mai.com, cpaasch@...le.com,
        David.Laight@...lab.com, ycheng@...gle.com
Subject: [PATCH 2/2] net: fastopen: use endianness agnostic representation of the cookie

Use an explicit little endian representation of the fastopen
cookie, so that the value no longer depends on the endianness
of the system. This fixes a theoretical issue only, since
fastopen keys are unlikely to be shared across load balancing
server farms that are mixed in endiannes, but it might pop up
in validation/selftests as well, so let's just settle on little
endian across the board.

Note that this change only affects big endian systems.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 include/linux/tcp.h     |  2 +-
 net/ipv4/tcp_fastopen.c | 16 ++++++++--------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 3d3659c638a6..f3a85a7fb4b1 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -58,7 +58,7 @@ static inline unsigned int tcp_optlen(const struct sk_buff *skb)
 
 /* TCP Fast Open Cookie as stored in memory */
 struct tcp_fastopen_cookie {
-	u64	val[DIV_ROUND_UP(TCP_FASTOPEN_COOKIE_MAX, sizeof(u64))];
+	__le64	val[DIV_ROUND_UP(TCP_FASTOPEN_COOKIE_MAX, sizeof(u64))];
 	s8	len;
 	bool	exp;	/* In RFC6994 experimental option format */
 };
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 61c15c3d3584..2704441a0bb0 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -123,10 +123,10 @@ static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
 	if (req->rsk_ops->family == AF_INET) {
 		const struct iphdr *iph = ip_hdr(syn);
 
-		foc->val[0] = siphash(&iph->saddr,
-				      sizeof(iph->saddr) +
-				      sizeof(iph->daddr),
-				      key);
+		foc->val[0] = cpu_to_le64(siphash(&iph->saddr,
+					  sizeof(iph->saddr) +
+					  sizeof(iph->daddr),
+					  key));
 		foc->len = TCP_FASTOPEN_COOKIE_SIZE;
 		return true;
 	}
@@ -134,10 +134,10 @@ static bool __tcp_fastopen_cookie_gen_cipher(struct request_sock *req,
 	if (req->rsk_ops->family == AF_INET6) {
 		const struct ipv6hdr *ip6h = ipv6_hdr(syn);
 
-		foc->val[0] = siphash(&ip6h->saddr,
-				      sizeof(ip6h->saddr) +
-				      sizeof(ip6h->daddr),
-				      key);
+		foc->val[0] = cpu_to_le64(siphash(&ip6h->saddr,
+					  sizeof(ip6h->saddr) +
+					  sizeof(ip6h->daddr),
+					  key));
 		foc->len = TCP_FASTOPEN_COOKIE_SIZE;
 		return true;
 	}
-- 
2.17.1