tunnel: drop packet if ECN present with not-ECT
Linux tunnels were written before RFC6040 and therefore never
implemented the corner case of ECN getting set in the outer header
and the inner header not being ready for it.
Section 4.2. Default Tunnel Egress Behaviour.
o If the inner ECN field is Not-ECT, the decapsulator MUST NOT
propagate any other ECN codepoint onwards. This is because the
inner Not-ECT marking is set by transports that rely on dropped
packets as an indication of congestion and would not understand or
respond to any other ECN codepoint [RFC4774]. Specifically:
* If the inner ECN field is Not-ECT and the outer ECN field is
CE, the decapsulator MUST drop the packet.
* If the inner ECN field is Not-ECT and the outer ECN field is
Not-ECT, ECT(0), or ECT(1), the decapsulator MUST forward the
outgoing packet with the ECN field cleared to Not-ECT.
This patch moves the ECN decap logic out of the individual tunnels
into a common place.
It also adds logging to allow detecting broken systems that
set ECN bits incorrectly when tunneling (or an intermediate
router might be changing the header).
Overloads rx_frame_error to keep track of ECN related error.
Thanks to Chris Wright who caught this while reviewing the new VXLAN
tunnel.
This code was tested by injecting faulty logic in other end GRE
to send incorrectly encapsulated packets.
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index b987d4d..613a166 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -56,6 +56,10 @@
#include <net/ip6_tunnel.h>
+static bool log_ecn_error = true;
+module_param(log_ecn_error, bool, 0644);
+MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");
+
#define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
#define IPV6_TCLASS_SHIFT 20
@@ -149,7 +153,9 @@
tot->rx_crc_errors = dev->stats.rx_crc_errors;
tot->rx_fifo_errors = dev->stats.rx_fifo_errors;
tot->rx_length_errors = dev->stats.rx_length_errors;
+ tot->rx_frame_errors = dev->stats.rx_frame_errors;
tot->rx_errors = dev->stats.rx_errors;
+
tot->tx_fifo_errors = dev->stats.tx_fifo_errors;
tot->tx_carrier_errors = dev->stats.tx_carrier_errors;
tot->tx_dropped = dev->stats.tx_dropped;
@@ -489,28 +495,6 @@
t->err_time = jiffies;
}
-static inline void ip6gre_ecn_decapsulate_ipv4(const struct ip6_tnl *t,
- const struct ipv6hdr *ipv6h, struct sk_buff *skb)
-{
- __u8 dsfield = ipv6_get_dsfield(ipv6h) & ~INET_ECN_MASK;
-
- if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
- ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, dsfield);
-
- if (INET_ECN_is_ce(dsfield))
- IP_ECN_set_ce(ip_hdr(skb));
-}
-
-static inline void ip6gre_ecn_decapsulate_ipv6(const struct ip6_tnl *t,
- const struct ipv6hdr *ipv6h, struct sk_buff *skb)
-{
- if (t->parms.flags & IP6_TNL_F_RCV_DSCP_COPY)
- ipv6_copy_dscp(ipv6_get_dsfield(ipv6h), ipv6_hdr(skb));
-
- if (INET_ECN_is_ce(ipv6_get_dsfield(ipv6h)))
- IP6_ECN_set_ce(ipv6_hdr(skb));
-}
-
static int ip6gre_rcv(struct sk_buff *skb)
{
const struct ipv6hdr *ipv6h;
@@ -522,6 +506,7 @@
struct ip6_tnl *tunnel;
int offset = 4;
__be16 gre_proto;
+ int err;
if (!pskb_may_pull(skb, sizeof(struct in6_addr)))
goto drop;
@@ -625,20 +610,29 @@
skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
}
+ __skb_tunnel_rx(skb, tunnel->dev);
+
+ skb_reset_network_header(skb);
+
+ err = IP6_ECN_decapsulate(ipv6h, skb);
+ if (unlikely(err)) {
+ if (log_ecn_error)
+ net_info_ratelimited("non-ECT from %pI6 with dsfield=%#x\n",
+ &ipv6h->saddr,
+ ipv6_get_dsfield(ipv6h));
+ if (err > 1) {
+ ++tunnel->dev->stats.rx_frame_errors;
+ ++tunnel->dev->stats.rx_errors;
+ goto drop;
+ }
+ }
+
tstats = this_cpu_ptr(tunnel->dev->tstats);
u64_stats_update_begin(&tstats->syncp);
tstats->rx_packets++;
tstats->rx_bytes += skb->len;
u64_stats_update_end(&tstats->syncp);
- __skb_tunnel_rx(skb, tunnel->dev);
-
- skb_reset_network_header(skb);
- if (skb->protocol == htons(ETH_P_IP))
- ip6gre_ecn_decapsulate_ipv4(tunnel, ipv6h, skb);
- else if (skb->protocol == htons(ETH_P_IPV6))
- ip6gre_ecn_decapsulate_ipv6(tunnel, ipv6h, skb);
-
netif_rx(skb);
return 0;