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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

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@linaro.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