netdev - [PATCH net] ipv6: drop packets with multiple fragmentation headers

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Message-ID: <20130816113007.GD2112@order.stressinduktion.org>
Date:	Fri, 16 Aug 2013 13:30:07 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	netdev@...r.kernel.org
Cc:	yoshfuji@...ux-ipv6.org
Subject: [PATCH net] ipv6: drop packets with multiple fragmentation headers

It is not allowed for an ipv6 packet to contain multiple fragmentation
headers. So discard packets which were already reassembled by
fragmentation logic and send back a parameter problem icmp.

The updates for RFC 6980 will come in later, I have to do a bit more
research here.

Cc: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 include/linux/ipv6.h  | 1 +
 net/ipv6/reassembly.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 77a4784..9ac5047 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -103,6 +103,7 @@ struct inet6_skb_parm {
 #define IP6SKB_FORWARDED	2
 #define IP6SKB_REROUTED		4
 #define IP6SKB_ROUTERALERT	8
+#define IP6SKB_FRAGMENTED      16
 };
 
 #define IP6CB(skb)	((struct inet6_skb_parm*)((skb)->cb))
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 790d9f4..1aeb473 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -490,6 +490,7 @@ static int ip6_frag_reasm(struct frag_queue *fq, struct sk_buff *prev,
 	ipv6_hdr(head)->payload_len = htons(payload_len);
 	ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);
 	IP6CB(head)->nhoff = nhoff;
+	IP6CB(head)->flags |= IP6SKB_FRAGMENTED;
 
 	/* Yes, and fold redundant checksum back. 8) */
 	if (head->ip_summed == CHECKSUM_COMPLETE)
@@ -524,6 +525,9 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 	struct net *net = dev_net(skb_dst(skb)->dev);
 	int evicted;
 
+	if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED)
+		goto fail_hdr;
+
 	IP6_INC_STATS_BH(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMREQDS);
 
 	/* Jumbo payload inhibits frag. header */
@@ -544,6 +548,7 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
 				 ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_REASMOKS);
 
 		IP6CB(skb)->nhoff = (u8 *)fhdr - skb_network_header(skb);
+		IP6CB(skb)->flags |= IP6SKB_FRAGMENTED;
 		return 1;
 	}
 
-- 
1.8.3.1

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