ipsec: IPSec interface correct drop w/ no protection

Type: improvement

When an IPSec interface is first constructed, the end node of the feature arc is not changed, which means it is interface-output.
This means that traffic directed into adjacencies on the link, that do not have protection (w/ an SA), drop like this:

...
00:00:01:111710: ip4-midchain
  tx_sw_if_index 4 dpo-idx 24 : ipv4 via 0.0.0.0 ipsec0: mtu:9000 next:6 flags:[]
  stacked-on:
    [@1]: dpo-drop ip4 flow hash: 0x00000000
  00000000: 4500005c000100003f01cb8cac100202010101010800ecf40000000058585858
  00000020: 58585858585858585858585858585858585858585858585858585858
00:00:01:111829: local0-output
  ipsec0
  00000000: 4500005c000100003f01cb8cac100202010101010800ecf40000000058585858
  00000020: 5858585858585858585858585858585858585858585858585858585858585858
  00000040: 58585858585858585858585858585858585858585858585858585858c2cf08c0
  00000060: 2a2c103cd0126bd8b03c4ec20ce2bd02dd77b3e3a4f49664
00:00:01:112017: error-drop
  rx:pg1
00:00:01:112034: drop
  local0-output: interface is down

although that's a drop, no packets should go to local0, and we want all IPvX packets to go through ipX-drop.

This change sets the interface's end-arc node to the appropriate drop node when the interface is created, and when the last protection is removed.
The resulting drop is:

...
00:00:01:111504: ip4-midchain
  tx_sw_if_index 4 dpo-idx 24 : ipv4 via 0.0.0.0 ipsec0: mtu:9000 next:0 flags:[]
  stacked-on:
    [@1]: dpo-drop ip4 flow hash: 0x00000000
  00000000: 4500005c000100003f01cb8cac100202010101010800ecf40000000058585858
  00000020: 58585858585858585858585858585858585858585858585858585858
00:00:01:111533: ip4-drop
    ICMP: 172.16.2.2 -> 1.1.1.1
      tos 0x00, ttl 63, length 92, checksum 0xcb8c dscp CS0 ecn NON_ECN
      fragment id 0x0001
    ICMP echo_request checksum 0xecf4 id 0
00:00:01:111620: error-drop
  rx:pg1
00:00:01:111640: drop
  null-node: blackholed packets

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: I7e7de23c541d9f1210a05e6984a688f1f821a155

1 files changed, 16 insertions, 0 deletions

diff --git a/src/vnet/ipsec/ipsec_itf.c b/src/vnet/ipsec/ipsec_itf.c
index fc0bf85a517..f9c1d77a37d 100644
--- a/src/vnet/ipsec/ipsec_itf.c
+++ b/src/vnet/ipsec/ipsec_itf.c
@@ -21,6 +21,7 @@
 #include <vnet/ipsec/ipsec.h>
 #include <vnet/adj/adj_midchain.h>
 #include <vnet/ethernet/mac_address.h>
+#include <vnet/mpls/mpls.h>
 
 /* bitmap of Allocated IPSEC_ITF instances */
 static uword *ipsec_itf_instances;
@@ -274,6 +275,20 @@ ipsec_itf_instance_free (u32 instance)
   return 0;
 }
 
+void
+ipsec_itf_reset_tx_nodes (u32 sw_if_index)
+{
+  vnet_feature_modify_end_node (
+    ip4_main.lookup_main.output_feature_arc_index, sw_if_index,
+    vlib_get_node_by_name (vlib_get_main (), (u8 *) "ip4-drop")->index);
+  vnet_feature_modify_end_node (
+    ip6_main.lookup_main.output_feature_arc_index, sw_if_index,
+    vlib_get_node_by_name (vlib_get_main (), (u8 *) "ip6-drop")->index);
+  vnet_feature_modify_end_node (
+    mpls_main.output_feature_arc_index, sw_if_index,
+    vlib_get_node_by_name (vlib_get_main (), (u8 *) "mpls-drop")->index);
+}
+
 int
 ipsec_itf_create (u32 user_instance, tunnel_mode_t mode, u32 * sw_if_indexp)
 {
@@ -318,6 +333,7 @@ ipsec_itf_create (u32 user_instance, tunnel_mode_t mode, u32 * sw_if_indexp)
   ipsec_itf_index_by_sw_if_index[hi->sw_if_index] = t_idx;
 
   ipsec_itf->ii_sw_if_index = *sw_if_indexp = hi->sw_if_index;
+  ipsec_itf_reset_tx_nodes (hi->sw_if_index);
 
   return 0;
 }