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| 1 | +/* |
| 2 | + * Copyright (c) 2009 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 "packets.h" |
| 19 | +#include <netinet/in.h> |
| 20 | +#include "ofpbuf.h" |
| 21 | + |
| 22 | +/* Fills 'b' with an 802.2 SNAP packet with Ethernet source address 'eth_src', |
| 23 | + * the Nicira OUI as SNAP organization and 'snap_type' as SNAP type. The text |
| 24 | + * string in 'tag' is enclosed as the packet payload. |
| 25 | + * |
| 26 | + * This function is used by Open vSwitch to compose packets in cases where |
| 27 | + * context is important but content doesn't (or shouldn't) matter. For this |
| 28 | + * purpose, 'snap_type' should be a random number and 'tag' should be an |
| 29 | + * English phrase that explains the purpose of the packet. (The English phrase |
| 30 | + * gives hapless admins running Wireshark the opportunity to figure out what's |
| 31 | + * going on.) */ |
| 32 | +void |
| 33 | +compose_benign_packet(struct ofpbuf *b, const char *tag, uint16_t snap_type, |
| 34 | + const uint8_t eth_src[ETH_ADDR_LEN]) |
| 35 | +{ |
| 36 | + struct eth_header *eth; |
| 37 | + struct llc_snap_header *llc_snap; |
| 38 | + |
| 39 | + /* Compose basic packet structure. (We need the payload size to stick into |
| 40 | + * the 802.2 header.) */ |
| 41 | + ofpbuf_clear(b); |
| 42 | + eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN); |
| 43 | + llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN); |
| 44 | + ofpbuf_put(b, tag, strlen(tag) + 1); /* Includes null byte. */ |
| 45 | + ofpbuf_put(b, eth_src, ETH_ADDR_LEN); |
| 46 | + |
| 47 | + /* Compose 802.2 header. */ |
| 48 | + memcpy(eth->eth_dst, eth_addr_broadcast, ETH_ADDR_LEN); |
| 49 | + memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN); |
| 50 | + eth->eth_type = htons(b->size - ETH_HEADER_LEN); |
| 51 | + |
| 52 | + /* Compose LLC, SNAP headers. */ |
| 53 | + llc_snap->llc.llc_dsap = LLC_DSAP_SNAP; |
| 54 | + llc_snap->llc.llc_ssap = LLC_SSAP_SNAP; |
| 55 | + llc_snap->llc.llc_cntl = LLC_CNTL_SNAP; |
| 56 | + memcpy(llc_snap->snap.snap_org, "\x00\x23\x20", 3); |
| 57 | + llc_snap->snap.snap_type = htons(snap_type); |
| 58 | +} |
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