[ovs-dev] [PATCH] ofproto-dpif: Fix for recirc issue with mpls traffic with dp_hash

Surya Rudra rudrasurya.r at altencalsoftlabs.com
Fri Jul 19 05:35:19 UTC 2019


Fix infinite recirculation loop for MPLS packets sent to dp_hash-based
 select group

Issue:
When a MPLS encapsulated packet is received, the MPLS header is removed,
a recirculation id assigned and then recirculated into the pipeline.
If the flow rules require the packet to be then sent over DP-HASH based
select group buckets, the packet has to be recirculated again. However,
the same recirculation id was used and this resulted in the packet being
repeatedly recirculated until it got dropped because the maximum recirculation
limit was hit.

Fix:
Include the  “was_mpls” boolean which indicates whether the packet was MPLS
encapsulated when computing the hash. After popping the MPLS header this will
result in a  different hash value than before and new recirculation id will
get generated.

DPCTL flows with and without the fix are shown below
Without Fix:
recirc_id(0x1),dp_hash(0x5194bf18/0xf),in_port(2),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:20, bytes:1960,
used:0.329s, actions:1
recirc_id(0x1),in_port(2),packet_type(ns=0,id=0),eth_type(0x0800),
ipv4(frag=no), packets:20, bytes:1960, used:0.329s,
actions:hash(sym_l4(0)),recirc(0x1)
recirc_id(0),in_port(2),packet_type(ns=0,id=0),eth_type(0x8847),
mpls(label=22/0xfffff,tc=0/0,ttl=64/0x0,bos=1/1), packets:20, bytes:2040,
used:0.329s, actions:pop_mpls(eth_type=0x800),recirc(0x1)

With Fix:
recirc_id(0x2),dp_hash(0x5194bf18/0xf),in_port(3),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:12481, bytes:1223138,
used:0.588s, actions:1
recirc_id(0x1),in_port(3),packet_type(ns=0,id=0),eth_type(0x0800),
ipv4(frag=no), packets:74431, bytes:7294238, used:0.386s,
actions:hash(sym_l4(0)),recirc(0x2)
recirc_id(0x2),dp_hash(0xb952470d/0xf),in_port(3),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:12441, bytes:1219218,
used:0.482s, actions:1
recirc_id(0x2),dp_hash(0xeff6ad76/0xf),in_port(3),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:12385, bytes:1213730,
used:0.908s, actions:1
recirc_id(0),in_port(3),packet_type(ns=0,id=0),eth_type(0x8847),
mpls(label=22/0xfffff,tc=0/0,ttl=64/0x0,bos=1/1), packets:74431,
bytes:7591962, used:0.386s, actions:pop_mpls(eth_type=0x800),recirc(0x1)
recirc_id(0x2),dp_hash(0xb6233fbe/0xf),in_port(3),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:12369, bytes:1212162,
used:0.386s, actions:1
recirc_id(0x2),dp_hash(0xa3670459/0xf),in_port(3),packet_type(ns=0,id=0),
eth_type(0x0800),ipv4(frag=no), packets:24751, bytes:2425598,
used:0.483s, actions:1

Signed-off-by: Surya Rudra <rudrasurya.r at altencalsoftlabs.com>
---
 ofproto/ofproto-dpif-rid.c   | 2 ++
 ofproto/ofproto-dpif-rid.h   | 1 +
 ofproto/ofproto-dpif-xlate.c | 2 ++
 3 files changed, 5 insertions(+)

diff --git a/ofproto/ofproto-dpif-rid.c b/ofproto/ofproto-dpif-rid.c
index 79412c2..29aafc2 100644
--- a/ofproto/ofproto-dpif-rid.c
+++ b/ofproto/ofproto-dpif-rid.c
@@ -130,6 +130,7 @@ frozen_state_hash(const struct frozen_state *state)
     hash = hash_bytes64((const uint64_t *) &state->metadata,
                         sizeof state->metadata, hash);
     hash = hash_boolean(state->conntracked, hash);
+    hash = hash_boolean(state->was_mpls, hash);
     if (state->stack && state->stack_size) {
         hash = hash_bytes(state->stack, state->stack_size, hash);
     }
@@ -158,6 +159,7 @@ frozen_state_equal(const struct frozen_state *a, const struct frozen_state *b)
             && !memcmp(a->stack, b->stack, a->stack_size)
             && a->mirrors == b->mirrors
             && a->conntracked == b->conntracked
+            && a->was_mpls == b->was_mpls
             && ofpacts_equal(a->ofpacts, a->ofpacts_len,
                              b->ofpacts, b->ofpacts_len)
             && ofpacts_equal(a->action_set, a->action_set_len,
diff --git a/ofproto/ofproto-dpif-rid.h b/ofproto/ofproto-dpif-rid.h
index ab5b87a..147ef9c 100644
--- a/ofproto/ofproto-dpif-rid.h
+++ b/ofproto/ofproto-dpif-rid.h
@@ -143,6 +143,7 @@ struct frozen_state {
     size_t stack_size;
     mirror_mask_t mirrors;        /* Mirrors already output. */
     bool conntracked;             /* Conntrack occurred prior to freeze. */
+    bool was_mpls;                /* MPLS packet */
     struct uuid xport_uuid;       /* UUID of 1st port packet received on. */
 
     /* Actions to be translated when thawing. */
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 73966a4..d4edf9c 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -4764,6 +4764,7 @@ xlate_controller_action(struct xlate_ctx *ctx, int len,
         .stack_size = ctx->stack.size,
         .mirrors = ctx->mirrors,
         .conntracked = ctx->conntracked,
+        .was_mpls = ctx->was_mpls,
         .ofpacts = NULL,
         .ofpacts_len = 0,
         .action_set = NULL,
@@ -4838,6 +4839,7 @@ finish_freezing__(struct xlate_ctx *ctx, uint8_t table)
         .stack_size = ctx->stack.size,
         .mirrors = ctx->mirrors,
         .conntracked = ctx->conntracked,
+        .was_mpls = ctx->was_mpls,
         .xport_uuid = ctx->xin->xport_uuid,
         .ofpacts = ctx->frozen_actions.data,
         .ofpacts_len = ctx->frozen_actions.size,
-- 
2.7.4



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