Thread (30 messages) 30 messages, 9 authors, 2013-01-09

Re: [PATCH] pkt_sched: act_xt support new Xtables interface

From: Pablo Neira Ayuso <pablo@netfilter.org>
Date: 2012-12-24 13:12:39
Also in: netfilter-devel

Possibly related (same subject, not in this thread)

Hi Felix,

On Mon, Dec 24, 2012 at 12:49:16PM +0100, Felix Fietkau wrote:
quoted hunk ↗ jump to hunk
On 2012-12-24 12:34 PM, Jamal Hadi Salim wrote:
quoted
Some good news Yury.
I am told Felix Fietkau [off-list ref] (on CC) actually
already solved this issue and it is a feature in openwrt. I
cant find the code.

Felix - Yury is trying to retrieve skb->mark fields from
netfilter connmark. My understanding is you have written
such an action. Can you please point us to it - and any
reason you havent submitted this for inclusion in kernel
proper?
After I added it as an experiment, I got distracted with other projects
again and forgot about submitting it. Take a look at the code - if the
approach is reasonable, I'll submit this thing for inclusion soon.

- Felix
--- /dev/null
+++ b/net/sched/act_connmark.c
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2011 Felix Fietkau <nbd@openwrt.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/pkt_cls.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/act_api.h>
+
+#include <net/netfilter/nf_conntrack.h>
+#include <net/netfilter/nf_conntrack_core.h>
+
+#define TCA_ACT_CONNMARK	20
+
+#define CONNMARK_TAB_MASK     3
+static struct tcf_common *tcf_connmark_ht[CONNMARK_TAB_MASK + 1];
+static u32 connmark_idx_gen;
+static DEFINE_RWLOCK(connmark_lock);
+
+static struct tcf_hashinfo connmark_hash_info = {
+	.htab	=	tcf_connmark_ht,
+	.hmask	=	CONNMARK_TAB_MASK,
+	.lock	=	&connmark_lock,
+};
+
+static int tcf_connmark(struct sk_buff *skb, const struct tc_action *a,
+		       struct tcf_result *res)
+{
+	struct nf_conn *c;
+	enum ip_conntrack_info ctinfo;
+	int proto;
+	int r;
+
+	if (skb->protocol == htons(ETH_P_IP)) {
+		if (skb->len < sizeof(struct iphdr))
+			goto out;
+		proto = PF_INET;
+	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		if (skb->len < sizeof(struct ipv6hdr))
+			goto out;
+		proto = PF_INET6;
+	} else
+		goto out;
+
+	r = nf_conntrack_in(dev_net(skb->dev), proto, NF_INET_PRE_ROUTING, skb);
conntrack needs to see defragmented packets, you have to call
nf_defrag_ipv4 / _ipv6 respectively before that.

This also changes the semantics of the raw table in iptables since it
will now see packet with conntrack already attached. So this would
also break -j CT --notrack.

This needs more thinking. I can appreciate the value of calling
conntrack from different points of the packet traversal, but there are
a couple of thing we have to resolve before allowing that.
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