From: Phil Oester <kernel@xxxxxxxxxxxx>
As reported by Casper Gripenberg, in a bridged setup, using ip[6]t_REJECT
with the tcp-reset option sends out reset packets with the src MAC address
of the local bridge interface, instead of the MAC address of the intended
destination. This causes some routers/firewalls to drop the reset packet
as it appears to be spoofed. Fix this by bypassing ip[6]_local_out and
setting the MAC of the sender in the tcp reset packet.
This closes netfilter bugzilla #531.
Signed-off-by: Phil Oester <kernel@xxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
net/ipv4/netfilter/ipt_REJECT.c | 21 ++++++++++++++++++++-
net/ipv6/netfilter/ip6t_REJECT.c | 20 +++++++++++++++++++-
2 files changed, 39 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/netfilter/ipt_REJECT.c b/net/ipv4/netfilter/ipt_REJECT.c
index 04b18c1..b969131 100644
--- a/net/ipv4/netfilter/ipt_REJECT.c
+++ b/net/ipv4/netfilter/ipt_REJECT.c
@@ -119,7 +119,26 @@ static void send_reset(struct sk_buff *oldskb, int hook)
nf_ct_attach(nskb, oldskb);
- ip_local_out(nskb);
+#ifdef CONFIG_BRIDGE_NETFILTER
+ /* If we use ip_local_out for bridged traffic, the MAC source on
+ * the RST will be ours, instead of the destination's. This confuses
+ * some routers/firewalls, and they drop the packet. So we need to
+ * build the eth header using the original destination's MAC as the
+ * source, and send the RST packet directly.
+ */
+ if (oldskb->nf_bridge) {
+ struct ethhdr *oeth = eth_hdr(oldskb);
+ nskb->dev = oldskb->nf_bridge->physindev;
+ niph->tot_len = htons(nskb->len);
+ ip_send_check(niph);
+ if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
+ oeth->h_source, oeth->h_dest, nskb->len) < 0)
+ goto free_nskb;
+ dev_queue_xmit(nskb);
+ } else
+#endif
+ ip_local_out(nskb);
+
return;
free_nskb:
diff --git a/net/ipv6/netfilter/ip6t_REJECT.c b/net/ipv6/netfilter/ip6t_REJECT.c
index 70f9abc..56eef30 100644
--- a/net/ipv6/netfilter/ip6t_REJECT.c
+++ b/net/ipv6/netfilter/ip6t_REJECT.c
@@ -169,7 +169,25 @@ static void send_reset(struct net *net, struct sk_buff *oldskb)
nf_ct_attach(nskb, oldskb);
- ip6_local_out(nskb);
+#ifdef CONFIG_BRIDGE_NETFILTER
+ /* If we use ip6_local_out for bridged traffic, the MAC source on
+ * the RST will be ours, instead of the destination's. This confuses
+ * some routers/firewalls, and they drop the packet. So we need to
+ * build the eth header using the original destination's MAC as the
+ * source, and send the RST packet directly.
+ */
+ if (oldskb->nf_bridge) {
+ struct ethhdr *oeth = eth_hdr(oldskb);
+ nskb->dev = oldskb->nf_bridge->physindev;
+ nskb->protocol = htons(ETH_P_IPV6);
+ ip6h->payload_len = htons(sizeof(struct tcphdr));
+ if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
+ oeth->h_source, oeth->h_dest, nskb->len) < 0)
+ return;
+ dev_queue_xmit(nskb);
+ } else
+#endif
+ ip6_local_out(nskb);
}
static inline void
--
1.7.10.4
--
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