[PATCH] sysctl_tcp_cookie_size read once

[William Allen Simpson]

Read sysctl_tcp_cookie_size only once in tcp_cookie_size_check(),
as it might be concurrently changed by another cpu.

Signed-off-by: William.Allen.Simpson@xxxxxxxxx
---
 net/ipv4/tcp_output.c |   15 +++++++++------
 1 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index de3bd84..49be4e3 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -392,27 +392,30 @@ struct tcp_out_options {
  */
 static u8 tcp_cookie_size_check(u8 desired)
 {
+	int cookie_size;
+
 	if (desired > 0) {
 		/* previously specified */
 		return desired;
 	}
-	if (sysctl_tcp_cookie_size <= 0) {
+	cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size);
+	if (cookie_size <= 0) {
 		/* no default specified */
 		return 0;
 	}
-	if (sysctl_tcp_cookie_size <= TCP_COOKIE_MIN) {
+	if (cookie_size <= TCP_COOKIE_MIN) {
 		/* value too small, specify minimum */
 		return TCP_COOKIE_MIN;
 	}
-	if (sysctl_tcp_cookie_size >= TCP_COOKIE_MAX) {
+	if (cookie_size >= TCP_COOKIE_MAX) {
 		/* value too large, specify maximum */
 		return TCP_COOKIE_MAX;
 	}
-	if (0x1 & sysctl_tcp_cookie_size) {
+	if (cookie_size & 0x1) {
 		/* 8-bit multiple, illegal, fix it */
-		return (u8)(sysctl_tcp_cookie_size + 0x1);
+		cookie_size += 0x1;
 	}
-	return (u8)sysctl_tcp_cookie_size;
+	return (u8)cookie_size;
 }
 
 /* Write previously computed TCP options to the packet.
-- 
1.7.1


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