From 9bb268ed7c5f0ec76a5bd6824450a104231152ba Mon Sep 17 00:00:00 2001 From: Jan Engelhardt Date: Mon, 14 Jan 2008 23:32:37 -0800 Subject: [PATCH] [NETFILTER]: xt_TOS: Change semantic of mask value This patch changes the behavior of xt_TOS v1 so that the mask value the user supplies means "zero out these bits" rather than "keep these bits". This is more easy on the user, as (I would assume) people keep more bits than zeroing, so, an example: Action: Set bit 0x01. before (&): iptables -j TOS --set-tos 0x01/0xFE after (&~): iptables -j TOS --set-tos 0x01/0x01 This is not too "tragic" with xt_TOS, but where larger fields are used (e.g. proposed xt_MARK v2), `--set-xmar 0x01/0x01` vs. `--set-xmark 0x01/0xFFFFFFFE` really makes a difference. Other target(!) modules, such as xt_TPROXY also use &~ rather than &, so let's get to a common ground. (Since xt_TOS has not yet left the development tree en direction to mainline, the semantic can be changed as proposed without breaking iptables.) Signed-off-by: Jan Engelhardt Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- net/netfilter/xt_DSCP.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/netfilter/xt_DSCP.c b/net/netfilter/xt_DSCP.c index fd7500ecadfd..9951e7f85e32 100644 --- a/net/netfilter/xt_DSCP.c +++ b/net/netfilter/xt_DSCP.c @@ -128,7 +128,7 @@ tos_tg(struct sk_buff *skb, const struct net_device *in, u_int8_t orig, nv; orig = ipv4_get_dsfield(iph); - nv = (orig & info->tos_mask) ^ info->tos_value; + nv = (orig & ~info->tos_mask) ^ info->tos_value; if (orig != nv) { if (!skb_make_writable(skb, sizeof(struct iphdr))) -- 2.20.1