ofproto/pktbuf.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "pktbuf.h"
  19 #include <inttypes.h>
  20 #include <stdlib.h>
  21 #include "coverage.h"
  22 #include "ofp-util.h"
  23 #include "ofpbuf.h"
  24 #include "timeval.h"
  25 #include "util.h"
  26 #include "vconn.h"
  27 #include "vlog.h"
  28
  29 VLOG_DEFINE_THIS_MODULE(pktbuf);
  30
  31 COVERAGE_DEFINE(pktbuf_buffer_unknown);
  32 COVERAGE_DEFINE(pktbuf_null_cookie);
  33 COVERAGE_DEFINE(pktbuf_retrieved);
  34 COVERAGE_DEFINE(pktbuf_reuse_error);
  35
  36 /* Buffers are identified by a 32-bit opaque ID.  We divide the ID
  37  * into a buffer number (low bits) and a cookie (high bits).  The buffer number
  38  * is an index into an array of buffers.  The cookie distinguishes between
  39  * different packets that have occupied a single buffer.  Thus, the more
  40  * buffers we have, the lower-quality the cookie... */
  41 #define PKTBUF_BITS     8
  42 #define PKTBUF_MASK     (PKTBUF_CNT - 1)
  43 #define PKTBUF_CNT      (1u << PKTBUF_BITS)
  44
  45 #define COOKIE_BITS     (32 - PKTBUF_BITS)
  46 #define COOKIE_MAX      ((1u << COOKIE_BITS) - 1)
  47
  48 #define OVERWRITE_MSECS 5000
  49
  50 struct packet {
  51     struct ofpbuf *buffer;
  52     uint32_t cookie;
  53     long long int timeout;
  54     ofp_port_t in_port;
  55 };
  56
  57 struct pktbuf {
  58     struct packet packets[PKTBUF_CNT];
  59     unsigned int buffer_idx;
  60     unsigned int null_idx;
  61 };
  62
  63 int
  64 pktbuf_capacity(void)
  65 {
  66     return PKTBUF_CNT;
  67 }
  68
  69 struct pktbuf *
  70 pktbuf_create(void)
  71 {
  72     return xzalloc(sizeof *pktbuf_create());
  73 }
  74
  75 void
  76 pktbuf_destroy(struct pktbuf *pb)
  77 {
  78     if (pb) {
  79         size_t i;
  80
  81         for (i = 0; i < PKTBUF_CNT; i++) {
  82             ofpbuf_delete(pb->packets[i].buffer);
  83         }
  84         free(pb);
  85     }
  86 }
  87
  88 static unsigned int
  89 make_id(unsigned int buffer_idx, unsigned int cookie)
  90 {
  91     return buffer_idx | (cookie << PKTBUF_BITS);
  92 }
  93
  94 /* Attempts to allocate an OpenFlow packet buffer id within 'pb'.  The packet
  95  * buffer will store a copy of 'buffer_size' bytes in 'buffer' and the port
  96  * number 'in_port', which should be the OpenFlow port number on which 'buffer'
  97  * was received.
  98  *
  99  * If successful, returns the packet buffer id (a number other than
 100  * UINT32_MAX).  pktbuf_retrieve() can later be used to retrieve the buffer and
 101  * its input port number (buffers do expire after a time, so this is not
 102  * guaranteed to be true forever).  On failure, returns UINT32_MAX.
 103  *
 104  * The caller retains ownership of 'buffer'. */
 105 uint32_t
 106 pktbuf_save(struct pktbuf *pb, const void *buffer, size_t buffer_size,
 107             ofp_port_t in_port)
 108 {
 109     struct packet *p = &pb->packets[pb->buffer_idx];
 110     pb->buffer_idx = (pb->buffer_idx + 1) & PKTBUF_MASK;
 111     if (p->buffer) {
 112         if (time_msec() < p->timeout) {
 113             return UINT32_MAX;
 114         }
 115         ofpbuf_delete(p->buffer);
 116     }
 117
 118     /* Don't use maximum cookie value since all-1-bits ID is special. */
 119     if (++p->cookie >= COOKIE_MAX) {
 120         p->cookie = 0;
 121     }
 122
 123     /* Use 2 bytes of headroom to 32-bit align the L3 header. */
 124     p->buffer = ofpbuf_clone_data_with_headroom(buffer, buffer_size, 2);
 125
 126     p->timeout = time_msec() + OVERWRITE_MSECS;
 127     p->in_port = in_port;
 128     return make_id(p - pb->packets, p->cookie);
 129 }
 130
 131 /*
 132  * Allocates and returns a "null" packet buffer id.  The returned packet buffer
 133  * id is considered valid by pktbuf_retrieve(), but it is not associated with
 134  * actual buffered data.
 135  *
 136  * This function is always successful.
 137  *
 138  * This is useful in one special case: with the current OpenFlow design, the
 139  * "fail-open" code cannot always know whether a connection to a controller is
 140  * actually valid until it receives a OFPT_PACKET_OUT or OFPT_FLOW_MOD request,
 141  * but at that point the packet in question has already been forwarded (since
 142  * we are still in "fail-open" mode).  If the packet was buffered in the usual
 143  * way, then the OFPT_PACKET_OUT or OFPT_FLOW_MOD would cause a duplicate
 144  * packet in the network.  Null packet buffer ids identify such a packet that
 145  * has already been forwarded, so that Open vSwitch can quietly ignore the
 146  * request to re-send it.  (After that happens, the switch exits fail-open
 147  * mode.)
 148  *
 149  * See the top-level comment in fail-open.c for an overview.
 150  */
 151 uint32_t
 152 pktbuf_get_null(void)
 153 {
 154     return make_id(0, COOKIE_MAX);
 155 }
 156
 157 /* Attempts to retrieve a saved packet with the given 'id' from 'pb'.  Returns
 158  * 0 if successful, otherwise an OpenFlow error code.
 159  *
 160  * On success, ordinarily stores the buffered packet in '*bufferp' and the
 161  * OpenFlow port number on which the packet was received in '*in_port'.  The
 162  * caller becomes responsible for freeing the buffer.  However, if 'id'
 163  * identifies a "null" packet buffer (created with pktbuf_get_null()), stores
 164  * NULL in '*bufferp' and OFPP_NONE in '*in_port'.
 165  *
 166  * 'in_port' may be NULL if the input port is not of interest.
 167  *
 168  * The L3 header of a returned packet will be 32-bit aligned.
 169  *
 170  * On failure, stores NULL in in '*bufferp' and UINT16_MAX in '*in_port'. */
 171 enum ofperr
 172 pktbuf_retrieve(struct pktbuf *pb, uint32_t id, struct ofpbuf **bufferp,
 173                 ofp_port_t *in_port)
 174 {
 175     static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 20);
 176     struct packet *p;
 177     enum ofperr error;
 178
 179     if (id == UINT32_MAX) {
 180         error = 0;
 181         goto error;
 182     }
 183
 184     if (!pb) {
 185         VLOG_WARN_RL(&rl, "attempt to send buffered packet via connection "
 186                      "without buffers");
 187         return OFPERR_OFPBRC_BUFFER_UNKNOWN;
 188     }
 189
 190     p = &pb->packets[id & PKTBUF_MASK];
 191     if (p->cookie == id >> PKTBUF_BITS) {
 192         struct ofpbuf *buffer = p->buffer;
 193         if (buffer) {
 194             *bufferp = buffer;
 195             if (in_port) {
 196                 *in_port = p->in_port;
 197             }
 198             p->buffer = NULL;
 199             COVERAGE_INC(pktbuf_retrieved);
 200             return 0;
 201         } else {
 202             COVERAGE_INC(pktbuf_reuse_error);
 203             VLOG_WARN_RL(&rl, "attempt to reuse buffer %08"PRIx32, id);
 204             error = OFPERR_OFPBRC_BUFFER_EMPTY;
 205         }
 206     } else if (id >> PKTBUF_BITS != COOKIE_MAX) {
 207         COVERAGE_INC(pktbuf_buffer_unknown);
 208         VLOG_WARN_RL(&rl, "cookie mismatch: %08"PRIx32" != %08"PRIx32,
 209                      id, (id & PKTBUF_MASK) | (p->cookie << PKTBUF_BITS));
 210         error = OFPERR_OFPBRC_BUFFER_UNKNOWN;
 211     } else {
 212         COVERAGE_INC(pktbuf_null_cookie);
 213         VLOG_INFO_RL(&rl, "Received null cookie %08"PRIx32" (this is normal "
 214                      "if the switch was recently in fail-open mode)", id);
 215         error = 0;
 216     }
 217 error:
 218     *bufferp = NULL;
 219     if (in_port) {
 220         *in_port = OFPP_NONE;
 221     }
 222     return error;
 223 }
 224
 225 void
 226 pktbuf_discard(struct pktbuf *pb, uint32_t id)
 227 {
 228     struct packet *p = &pb->packets[id & PKTBUF_MASK];
 229     if (p->cookie == id >> PKTBUF_BITS) {
 230         ofpbuf_delete(p->buffer);
 231         p->buffer = NULL;
 232     }
 233 }
 234
 235 /* Returns the number of packets buffered in 'pb'.  Returns 0 if 'pb' is
 236  * null. */
 237 unsigned int
 238 pktbuf_count_packets(const struct pktbuf *pb)
 239 {
 240     int n = 0;
 241
 242     if (pb) {
 243         int i;
 244
 245         for (i = 0; i < PKTBUF_CNT; i++) {
 246             if (pb->packets[i].buffer) {
 247                 n++;
 248             }
 249         }
 250     }
 251
 252     return n;
 253 }