mirror of
https://github.com/openvswitch/ovs
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59 lines
2.3 KiB
C
59 lines
2.3 KiB
C
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/*
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* Copyright (c) 2009 Nicira Networks.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "packets.h"
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#include <netinet/in.h>
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#include "ofpbuf.h"
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/* Fills 'b' with an 802.2 SNAP packet with Ethernet source address 'eth_src',
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* the Nicira OUI as SNAP organization and 'snap_type' as SNAP type. The text
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* string in 'tag' is enclosed as the packet payload.
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*
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* This function is used by Open vSwitch to compose packets in cases where
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* context is important but content doesn't (or shouldn't) matter. For this
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* purpose, 'snap_type' should be a random number and 'tag' should be an
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* English phrase that explains the purpose of the packet. (The English phrase
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* gives hapless admins running Wireshark the opportunity to figure out what's
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* going on.) */
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void
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compose_benign_packet(struct ofpbuf *b, const char *tag, uint16_t snap_type,
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const uint8_t eth_src[ETH_ADDR_LEN])
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{
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struct eth_header *eth;
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struct llc_snap_header *llc_snap;
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/* Compose basic packet structure. (We need the payload size to stick into
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* the 802.2 header.) */
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ofpbuf_clear(b);
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eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
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llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN);
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ofpbuf_put(b, tag, strlen(tag) + 1); /* Includes null byte. */
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ofpbuf_put(b, eth_src, ETH_ADDR_LEN);
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/* Compose 802.2 header. */
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memcpy(eth->eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
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memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
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eth->eth_type = htons(b->size - ETH_HEADER_LEN);
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/* Compose LLC, SNAP headers. */
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llc_snap->llc.llc_dsap = LLC_DSAP_SNAP;
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llc_snap->llc.llc_ssap = LLC_SSAP_SNAP;
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llc_snap->llc.llc_cntl = LLC_CNTL_SNAP;
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memcpy(llc_snap->snap.snap_org, "\x00\x23\x20", 3);
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llc_snap->snap.snap_type = htons(snap_type);
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}
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