decap.c

Go to the documentation of this file.

/*
 * decap.c : L2TPv3 tunnel decapsulation
 *
 * Copyright (c) 2013 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <vppinfra/error.h>
#include <vppinfra/hash.h>
#include <vnet/vnet.h>
#include <vnet/ip/ip.h>
#include <vnet/ethernet/ethernet.h>
#include <vnet/l2tp/l2tp.h>

/* Statistics (not really errors) */
#define foreach_l2t_decap_error                                   \
_(USER_TO_NETWORK, "L2TP user (ip6) to L2 network pkts")        \
_(SESSION_ID_MISMATCH, "l2tpv3 local session id mismatches")    \
_(COOKIE_MISMATCH, "l2tpv3 local cookie mismatches")  

static char * l2t_decap_error_strings[] = {
#define _(sym,string) string,
  foreach_l2t_decap_error
#undef _
};

typedef enum {
#define _(sym,str) L2T_DECAP_ERROR_##sym,
    foreach_l2t_decap_error
#undef _
    L2T_DECAP_N_ERROR,
} l2t_DECAP_error_t;

typedef enum { 
    L2T_DECAP_NEXT_DROP,
    L2T_DECAP_NEXT_L2_INPUT,
    L2T_DECAP_N_NEXT,
    /* Pseudo next index */
    L2T_DECAP_NEXT_NO_INTERCEPT = L2T_DECAP_N_NEXT,
} l2t_decap_next_t;

#define NSTAGES 3

static inline void stage0 (vlib_main_t * vm,
                           vlib_node_runtime_t * node,
                           u32 buffer_index)
{
    vlib_buffer_t *b = vlib_get_buffer (vm, buffer_index);
    vlib_prefetch_buffer_header (b, STORE);
    /* l2tpv3 header is a long way away, need 2 cache lines */
    CLIB_PREFETCH (b->data, 2*CLIB_CACHE_LINE_BYTES, STORE);
}

static inline void stage1 (vlib_main_t * vm,
                           vlib_node_runtime_t * node,
                           u32 bi)
{
    vlib_buffer_t *b = vlib_get_buffer (vm, bi);
    l2t_main_t *lm = &l2t_main;
    ip6_header_t * ip6 = vlib_buffer_get_current (b);
    u32 session_index;
    uword *p = 0;
    l2tpv3_header_t * l2t;

    /* Not L2tpv3 (0x73, 0t115)? Use the normal path. */
    if (PREDICT_FALSE(ip6->protocol != IP_PROTOCOL_L2TP)) {
        vnet_buffer(b)->l2t.next_index = L2T_DECAP_NEXT_NO_INTERCEPT;
        return;
    }

    /* Make up your minds, people... */
    switch (lm->lookup_type) {
    case L2T_LOOKUP_SRC_ADDRESS:
        p = hash_get_mem (lm->session_by_src_address, &ip6->src_address);
        break;
    case L2T_LOOKUP_DST_ADDRESS:
        p = hash_get_mem (lm->session_by_dst_address, &ip6->dst_address);
        break;
    case L2T_LOOKUP_SESSION_ID:
        l2t = (l2tpv3_header_t*)(ip6+1);
        p = hash_get (lm->session_by_session_id, l2t->session_id);
        break;
    default:
        ASSERT(0);
    }

    if (PREDICT_FALSE(p == 0)) {
        vnet_buffer(b)->l2t.next_index = L2T_DECAP_NEXT_NO_INTERCEPT;
        return;
    } else {
        session_index = p[0];
    }

    /* Remember mapping index, prefetch the mini counter */
    vnet_buffer(b)->l2t.next_index = L2T_DECAP_NEXT_L2_INPUT;
    vnet_buffer(b)->l2t.session_index = session_index;

    /* $$$$$ prefetch counter */
}

static inline u32 last_stage (vlib_main_t *vm, vlib_node_runtime_t *node,
                              u32 bi)
{
    vlib_buffer_t *b = vlib_get_buffer (vm, bi);
    l2t_main_t *lm = &l2t_main;
    ip6_header_t * ip6 = vlib_buffer_get_current (b);
    vlib_node_t *n = vlib_get_node (vm, l2t_decap_node.index);
    u32 node_counter_base_index = n->error_heap_index;
    vlib_error_main_t * em = &vm->error_main;
    l2tpv3_header_t * l2tp;
    u32 counter_index;
    l2t_session_t * session;
    u32 session_index;
    u32 next_index;
    
    /* Other-than-output pkt? We're done... */
    if (vnet_buffer(b)->l2t.next_index != L2T_DECAP_NEXT_L2_INPUT) {
      next_index = vnet_buffer(b)->l2t.next_index;
      goto done;
    }

    em->counters[node_counter_base_index + L2T_DECAP_ERROR_USER_TO_NETWORK] += 1;
    
    session_index = vnet_buffer(b)->l2t.session_index;

    counter_index = 
        session_index_to_counter_index (session_index,
                                        SESSION_COUNTER_USER_TO_NETWORK);

    /* per-mapping byte stats include the ethernet header */
    vlib_increment_combined_counter (&lm->counter_main, 
                                     os_get_cpu_number(),
                                     counter_index,
                                     1 /* packet_increment */,
                                     vlib_buffer_length_in_chain (vm, b) +
                                     sizeof (ethernet_header_t));
    
    session = pool_elt_at_index (lm->sessions, session_index);

    l2tp = vlib_buffer_get_current (b) + sizeof (*ip6);
    
    if (PREDICT_FALSE(l2tp->session_id != session->local_session_id)) {
      // Key matched but session id does not. Assume packet is not for us.
      em->counters[node_counter_base_index + L2T_DECAP_ERROR_SESSION_ID_MISMATCH] += 1;
      next_index = L2T_DECAP_NEXT_NO_INTERCEPT;
      goto done;
    }

    if (PREDICT_FALSE (l2tp->cookie != session->local_cookie[0])) {
        if (l2tp->cookie != session->local_cookie[1]) {
            // Key and session ID matched, but cookie doesn't. Drop this packet.
            b->error = node->errors[L2T_DECAP_ERROR_COOKIE_MISMATCH];
            next_index = L2T_DECAP_NEXT_DROP;
            goto done;
        }
    }

    vnet_buffer(b)->sw_if_index[VLIB_RX] = session->sw_if_index;

    /* strip the ip6 and L2TP header */
    vlib_buffer_advance (b, sizeof (*ip6) + session->l2tp_hdr_size);

    /* Required to make the l2 tag push / pop code work on l2 subifs */
    vnet_update_l2_len (b);

    if (PREDICT_FALSE(b->flags & VLIB_BUFFER_IS_TRACED)) {
        l2t_trace_t *t = vlib_add_trace (vm, node, b, sizeof (*t));
        t->is_user_to_network = 1;
        t->our_address.as_u64[0] = 
            ip6->dst_address.as_u64[0];
        t->our_address.as_u64[1] = 
            ip6->dst_address.as_u64[1];
        t->client_address.as_u64[0] = 
            ip6->src_address.as_u64[0];
        t->client_address.as_u64[1] = 
            ip6->src_address.as_u64[1];
        t->session_index = session_index;
    }

    return L2T_DECAP_NEXT_L2_INPUT;

 done:
   if (next_index == L2T_DECAP_NEXT_NO_INTERCEPT) {
      // Go to next node on the ip6 configuration chain
      ip6_main_t * im = &ip6_main;
      ip_lookup_main_t * lm = &im->lookup_main;
      ip_config_main_t * cm = &lm->rx_config_mains[VNET_UNICAST];
      ip6_l2tpv3_config_t * c0;

      vnet_get_config_data (&cm->config_main,
                            &vnet_buffer (b)->ip.current_config_index,
                            &next_index,
                            sizeof (c0[0]));
    }

    if (PREDICT_FALSE(b->flags & VLIB_BUFFER_IS_TRACED)) {
        l2t_trace_t *t = vlib_add_trace (vm, node, b, sizeof (*t));
        t->is_user_to_network = 1;
        t->our_address.as_u64[0] = 
            ip6->dst_address.as_u64[0];
        t->our_address.as_u64[1] = 
            ip6->dst_address.as_u64[1];
        t->client_address.as_u64[0] = 
            ip6->src_address.as_u64[0];
        t->client_address.as_u64[1] = 
            ip6->src_address.as_u64[1];
        t->session_index = ~0;
    }
    return next_index;
}

#include <vnet/pipeline.h>

static uword l2t_decap_node_fn (vlib_main_t * vm,
                              vlib_node_runtime_t * node,
                              vlib_frame_t * frame)
{
    return dispatch_pipeline (vm, node, frame);
}

VLIB_REGISTER_NODE (l2t_decap_node) = {
  .function = l2t_decap_node_fn,
  .name = "l2tp-decap",
  .vector_size = sizeof (u32),
  .format_trace = format_l2t_trace,
  .type = VLIB_NODE_TYPE_INTERNAL,
  
  .n_errors = ARRAY_LEN(l2t_decap_error_strings),
  .error_strings = l2t_decap_error_strings,

  .n_next_nodes = L2T_DECAP_N_NEXT,

  /* edit / add dispositions here */
  .next_nodes = {
        [L2T_DECAP_NEXT_L2_INPUT] = "l2-input",
        [L2T_DECAP_NEXT_DROP] = "error-drop",
  },
};

void l2tp_decap_init (void) 
{
  ip6_register_protocol (IP_PROTOCOL_L2TP, l2t_decap_node.index);
}