IPv6 NAT: Do not drop DNATed 6to4/6rd packets
When a router is doing DNAT for 6to4/6rd packets the latest
anti-spoofing commit 218774dc ("ipv6: add anti-spoofing checks for
6to4 and 6rd") will drop them because the IPv6 address embedded does
not match the IPv4 destination. This patch will allow them to pass by
testing if we have an address that matches on 6to4/6rd interface. I
have been hit by this problem using Fedora and IPV6TO4_IPV4ADDR.
Also, log the dropped packets (with rate limit).
Signed-off-by: Catalin(ux) M. BOIE <catab@embedromix.ro>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index fb314de..86505bf 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h
@@ -67,6 +67,10 @@
int ipv6_chk_home_addr(struct net *net, const struct in6_addr *addr);
#endif
+bool ipv6_chk_custom_prefix(const struct in6_addr *addr,
+ const unsigned int prefix_len,
+ struct net_device *dev);
+
int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev);
struct inet6_ifaddr *ipv6_get_ifaddr(struct net *net,
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index d6ff126..a0c3abe 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1499,6 +1499,33 @@
return false;
}
+/* Compares an address/prefix_len with addresses on device @dev.
+ * If one is found it returns true.
+ */
+bool ipv6_chk_custom_prefix(const struct in6_addr *addr,
+ const unsigned int prefix_len, struct net_device *dev)
+{
+ struct inet6_dev *idev;
+ struct inet6_ifaddr *ifa;
+ bool ret = false;
+
+ rcu_read_lock();
+ idev = __in6_dev_get(dev);
+ if (idev) {
+ read_lock_bh(&idev->lock);
+ list_for_each_entry(ifa, &idev->addr_list, if_list) {
+ ret = ipv6_prefix_equal(addr, &ifa->addr, prefix_len);
+ if (ret)
+ break;
+ }
+ read_unlock_bh(&idev->lock);
+ }
+ rcu_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL(ipv6_chk_custom_prefix);
+
int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev)
{
struct inet6_dev *idev;
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 7ee5cb9..afd5605 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -566,6 +566,70 @@
return false;
}
+/* Checks if an address matches an address on the tunnel interface.
+ * Used to detect the NAT of proto 41 packets and let them pass spoofing test.
+ * Long story:
+ * This function is called after we considered the packet as spoofed
+ * in is_spoofed_6rd.
+ * We may have a router that is doing NAT for proto 41 packets
+ * for an internal station. Destination a.a.a.a/PREFIX:bbbb:bbbb
+ * will be translated to n.n.n.n/PREFIX:bbbb:bbbb. And is_spoofed_6rd
+ * function will return true, dropping the packet.
+ * But, we can still check if is spoofed against the IP
+ * addresses associated with the interface.
+ */
+static bool only_dnatted(const struct ip_tunnel *tunnel,
+ const struct in6_addr *v6dst)
+{
+ int prefix_len;
+
+#ifdef CONFIG_IPV6_SIT_6RD
+ prefix_len = tunnel->ip6rd.prefixlen + 32
+ - tunnel->ip6rd.relay_prefixlen;
+#else
+ prefix_len = 48;
+#endif
+ return ipv6_chk_custom_prefix(v6dst, prefix_len, tunnel->dev);
+}
+
+/* Returns true if a packet is spoofed */
+static bool packet_is_spoofed(struct sk_buff *skb,
+ const struct iphdr *iph,
+ struct ip_tunnel *tunnel)
+{
+ const struct ipv6hdr *ipv6h;
+
+ if (tunnel->dev->priv_flags & IFF_ISATAP) {
+ if (!isatap_chksrc(skb, iph, tunnel))
+ return true;
+
+ return false;
+ }
+
+ if (tunnel->dev->flags & IFF_POINTOPOINT)
+ return false;
+
+ ipv6h = ipv6_hdr(skb);
+
+ if (unlikely(is_spoofed_6rd(tunnel, iph->saddr, &ipv6h->saddr))) {
+ net_warn_ratelimited("Src spoofed %pI4/%pI6c -> %pI4/%pI6c\n",
+ &iph->saddr, &ipv6h->saddr,
+ &iph->daddr, &ipv6h->daddr);
+ return true;
+ }
+
+ if (likely(!is_spoofed_6rd(tunnel, iph->daddr, &ipv6h->daddr)))
+ return false;
+
+ if (only_dnatted(tunnel, &ipv6h->daddr))
+ return false;
+
+ net_warn_ratelimited("Dst spoofed %pI4/%pI6c -> %pI4/%pI6c\n",
+ &iph->saddr, &ipv6h->saddr,
+ &iph->daddr, &ipv6h->daddr);
+ return true;
+}
+
static int ipip6_rcv(struct sk_buff *skb)
{
const struct iphdr *iph = ip_hdr(skb);
@@ -586,19 +650,9 @@
IPCB(skb)->flags = 0;
skb->protocol = htons(ETH_P_IPV6);
- if (tunnel->dev->priv_flags & IFF_ISATAP) {
- if (!isatap_chksrc(skb, iph, tunnel)) {
- tunnel->dev->stats.rx_errors++;
- goto out;
- }
- } else if (!(tunnel->dev->flags&IFF_POINTOPOINT)) {
- if (is_spoofed_6rd(tunnel, iph->saddr,
- &ipv6_hdr(skb)->saddr) ||
- is_spoofed_6rd(tunnel, iph->daddr,
- &ipv6_hdr(skb)->daddr)) {
- tunnel->dev->stats.rx_errors++;
- goto out;
- }
+ if (packet_is_spoofed(skb, iph, tunnel)) {
+ tunnel->dev->stats.rx_errors++;
+ goto out;
}
__skb_tunnel_rx(skb, tunnel->dev, tunnel->net);
@@ -748,7 +802,7 @@
neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
if (neigh == NULL) {
- net_dbg_ratelimited("sit: nexthop == NULL\n");
+ net_dbg_ratelimited("nexthop == NULL\n");
goto tx_error;
}
@@ -777,7 +831,7 @@
neigh = dst_neigh_lookup(skb_dst(skb), &iph6->daddr);
if (neigh == NULL) {
- net_dbg_ratelimited("sit: nexthop == NULL\n");
+ net_dbg_ratelimited("nexthop == NULL\n");
goto tx_error;
}