ofproto/pktbuf.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010 Nicira Networks.
   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 "ofpbuf.h"
  23 #include "timeval.h"
  24 #include "util.h"
  25 #include "vconn.h"
  26
  27 #define THIS_MODULE VLM_pktbuf
  28 #include "vlog.h"
  29
  30 /* Buffers are identified by a 32-bit opaque ID.  We divide the ID
  31  * into a buffer number (low bits) and a cookie (high bits).  The buffer number
  32  * is an index into an array of buffers.  The cookie distinguishes between
  33  * different packets that have occupied a single buffer.  Thus, the more
  34  * buffers we have, the lower-quality the cookie... */
  35 #define PKTBUF_BITS     8
  36 #define PKTBUF_MASK     (PKTBUF_CNT - 1)
  37 #define PKTBUF_CNT      (1u << PKTBUF_BITS)
  38
  39 #define COOKIE_BITS     (32 - PKTBUF_BITS)
  40 #define COOKIE_MAX      ((1u << COOKIE_BITS) - 1)
  41
  42 #define OVERWRITE_MSECS 5000
  43
  44 struct packet {
  45     struct ofpbuf *buffer;
  46     uint32_t cookie;
  47     long long int timeout;
  48     uint16_t in_port;
  49 };
  50
  51 struct pktbuf {
  52     struct packet packets[PKTBUF_CNT];
  53     unsigned int buffer_idx;
  54     unsigned int null_idx;
  55 };
  56
  57 int
  58 pktbuf_capacity(void)
  59 {
  60     return PKTBUF_CNT;
  61 }
  62
  63 struct pktbuf *
  64 pktbuf_create(void)
  65 {
  66     return xzalloc(sizeof *pktbuf_create());
  67 }
  68
  69 void
  70 pktbuf_destroy(struct pktbuf *pb)
  71 {
  72     if (pb) {
  73         size_t i;
  74
  75         for (i = 0; i < PKTBUF_CNT; i++) {
  76             ofpbuf_delete(pb->packets[i].buffer);
  77         }
  78         free(pb);
  79     }
  80 }
  81
  82 static unsigned int
  83 make_id(unsigned int buffer_idx, unsigned int cookie)
  84 {
  85     return buffer_idx | (cookie << PKTBUF_BITS);
  86 }
  87
  88 /* Attempts to allocate an OpenFlow packet buffer id within 'pb'.  The packet
  89  * buffer will store a copy of 'buffer' and the port number 'in_port', which
  90  * should be the datapath port number on which 'buffer' was received.
  91  *
  92  * If successful, returns the packet buffer id (a number other than
  93  * UINT32_MAX).  pktbuf_retrieve() can later be used to retrieve the buffer and
  94  * its input port number (buffers do expire after a time, so this is not
  95  * guaranteed to be true forever).  On failure, returns UINT32_MAX.
  96  *
  97  * The caller retains ownership of 'buffer'. */
  98 uint32_t
  99 pktbuf_save(struct pktbuf *pb, struct ofpbuf *buffer, uint16_t in_port)
 100 {
 101     struct packet *p = &pb->packets[pb->buffer_idx];
 102     pb->buffer_idx = (pb->buffer_idx + 1) & PKTBUF_MASK;
 103     if (p->buffer) {
 104         if (time_msec() < p->timeout) {
 105             return UINT32_MAX;
 106         }
 107         ofpbuf_delete(p->buffer);
 108     }
 109
 110     /* Don't use maximum cookie value since all-1-bits ID is special. */
 111     if (++p->cookie >= COOKIE_MAX) {
 112         p->cookie = 0;
 113     }
 114     p->buffer = ofpbuf_clone(buffer);
 115     p->timeout = time_msec() + OVERWRITE_MSECS;
 116     p->in_port = in_port;
 117     return make_id(p - pb->packets, p->cookie);
 118 }
 119
 120 /*
 121  * Allocates and returns a "null" packet buffer id.  The returned packet buffer
 122  * id is considered valid by pktbuf_retrieve(), but it is not associated with
 123  * actual buffered data.
 124  *
 125  * This function is always successful.
 126  *
 127  * This is useful in one special case: with the current OpenFlow design, the
 128  * "fail-open" code cannot always know whether a connection to a controller is
 129  * actually valid until it receives a OFPT_PACKET_OUT or OFPT_FLOW_MOD request,
 130  * but at that point the packet in question has already been forwarded (since
 131  * we are still in "fail-open" mode).  If the packet was buffered in the usual
 132  * way, then the OFPT_PACKET_OUT or OFPT_FLOW_MOD would cause a duplicate
 133  * packet in the network.  Null packet buffer ids identify such a packet that
 134  * has already been forwarded, so that Open vSwitch can quietly ignore the
 135  * request to re-send it.  (After that happens, the switch exits fail-open
 136  * mode.)
 137  *
 138  * See the top-level comment in fail-open.c for an overview.
 139  */
 140 uint32_t
 141 pktbuf_get_null(void)
 142 {
 143     return make_id(0, COOKIE_MAX);
 144 }
 145
 146 /* Attempts to retrieve a saved packet with the given 'id' from 'pb'.  Returns
 147  * 0 if successful, otherwise an OpenFlow error code constructed with
 148  * ofp_mkerr().
 149  *
 150  * On success, ordinarily stores the buffered packet in '*bufferp' and the
 151  * datapath port number on which the packet was received in '*in_port'.  The
 152  * caller becomes responsible for freeing the buffer.  However, if 'id'
 153  * identifies a "null" packet buffer (created with pktbuf_get_null()), stores
 154  * NULL in '*bufferp' and UINT16_max in '*in_port'.
 155  *
 156  * On failure, stores NULL in in '*bufferp' and UINT16_MAX in '*in_port'. */
 157 int
 158 pktbuf_retrieve(struct pktbuf *pb, uint32_t id, struct ofpbuf **bufferp,
 159                 uint16_t *in_port)
 160 {
 161     static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 20);
 162     struct packet *p;
 163     int error;
 164
 165     if (!pb) {
 166         VLOG_WARN_RL(&rl, "attempt to send buffered packet via connection "
 167                      "without buffers");
 168         return ofp_mkerr(OFPET_BAD_REQUEST, OFPBRC_BUFFER_UNKNOWN);
 169     }
 170
 171     p = &pb->packets[id & PKTBUF_MASK];
 172     if (p->cookie == id >> PKTBUF_BITS) {
 173         struct ofpbuf *buffer = p->buffer;
 174         if (buffer) {
 175             *bufferp = buffer;
 176             *in_port = p->in_port;
 177             p->buffer = NULL;
 178             COVERAGE_INC(pktbuf_retrieved);
 179             return 0;
 180         } else {
 181             COVERAGE_INC(pktbuf_reuse_error);
 182             VLOG_WARN_RL(&rl, "attempt to reuse buffer %08"PRIx32, id);
 183             error = ofp_mkerr(OFPET_BAD_REQUEST, OFPBRC_BUFFER_EMPTY);
 184         }
 185     } else if (id >> PKTBUF_BITS != COOKIE_MAX) {
 186         COVERAGE_INC(pktbuf_buffer_unknown);
 187         VLOG_WARN_RL(&rl, "cookie mismatch: %08"PRIx32" != %08"PRIx32,
 188                      id, (id & PKTBUF_MASK) | (p->cookie << PKTBUF_BITS));
 189         error = ofp_mkerr(OFPET_BAD_REQUEST, OFPBRC_BUFFER_UNKNOWN);
 190     } else {
 191         COVERAGE_INC(pktbuf_null_cookie);
 192         VLOG_INFO_RL(&rl, "Received null cookie %08"PRIx32" (this is normal "
 193                      "if the switch was recently in fail-open mode)", id);
 194         error = 0;
 195     }
 196     *bufferp = NULL;
 197     *in_port = UINT16_MAX;
 198     return error;
 199 }
 200
 201 void
 202 pktbuf_discard(struct pktbuf *pb, uint32_t id)
 203 {
 204     struct packet *p = &pb->packets[id & PKTBUF_MASK];
 205     if (p->cookie == id >> PKTBUF_BITS) {
 206         ofpbuf_delete(p->buffer);
 207         p->buffer = NULL;
 208     }
 209 }