ovs/lib/packets.c

/*
 * Copyright (c) 2009, 2010 Nicira Networks.
 *
 * 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 <config.h>
#include "packets.h"
#include <assert.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <stdlib.h>
#include "byte-order.h"
#include "dynamic-string.h"
#include "ofpbuf.h"

const struct in6_addr in6addr_exact = IN6ADDR_EXACT_INIT;

/* Parses 's' as a 16-digit hexadecimal number representing a datapath ID.  On
 * success stores the dpid into '*dpidp' and returns true, on failure stores 0
 * into '*dpidp' and returns false.
 *
 * Rejects an all-zeros dpid as invalid. */
bool
dpid_from_string(const char *s, uint64_t *dpidp)
{
    *dpidp = (strlen(s) == 16 && strspn(s, "0123456789abcdefABCDEF") == 16
              ? strtoull(s, NULL, 16)
              : 0);
    return *dpidp != 0;
}

bool
eth_addr_from_string(const char *s, uint8_t ea[ETH_ADDR_LEN])
{
    if (sscanf(s, ETH_ADDR_SCAN_FMT, ETH_ADDR_SCAN_ARGS(ea))
        == ETH_ADDR_SCAN_COUNT) {
        return true;
    } else {
        memset(ea, 0, ETH_ADDR_LEN);
        return false;
    }
}

/* Fills 'b' with an 802.2 SNAP packet with Ethernet source address 'eth_src',
 * the Nicira OUI as SNAP organization and 'snap_type' as SNAP type.  The text
 * string in 'tag' is enclosed as the packet payload.
 *
 * This function is used by Open vSwitch to compose packets in cases where
 * context is important but content doesn't (or shouldn't) matter.  For this
 * purpose, 'snap_type' should be a random number and 'tag' should be an
 * English phrase that explains the purpose of the packet.  (The English phrase
 * gives hapless admins running Wireshark the opportunity to figure out what's
 * going on.) */
void
compose_benign_packet(struct ofpbuf *b, const char *tag, uint16_t snap_type,
                      const uint8_t eth_src[ETH_ADDR_LEN])
{
    struct eth_header *eth;
    struct llc_snap_header *llc_snap;

    /* Compose basic packet structure.  (We need the payload size to stick into
     * the 802.2 header.) */
    ofpbuf_clear(b);
    eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
    llc_snap = ofpbuf_put_zeros(b, LLC_SNAP_HEADER_LEN);
    ofpbuf_put(b, tag, strlen(tag) + 1); /* Includes null byte. */
    ofpbuf_put(b, eth_src, ETH_ADDR_LEN);

    /* Compose 802.2 header. */
    memcpy(eth->eth_dst, eth_addr_broadcast, ETH_ADDR_LEN);
    memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
    eth->eth_type = htons(b->size - ETH_HEADER_LEN);

    /* Compose LLC, SNAP headers. */
    llc_snap->llc.llc_dsap = LLC_DSAP_SNAP;
    llc_snap->llc.llc_ssap = LLC_SSAP_SNAP;
    llc_snap->llc.llc_cntl = LLC_CNTL_SNAP;
    memcpy(llc_snap->snap.snap_org, "\x00\x23\x20", 3);
    llc_snap->snap.snap_type = htons(snap_type);
}

/* Stores the string representation of the IPv6 address 'addr' into the
 * character array 'addr_str', which must be at least INET6_ADDRSTRLEN
 * bytes long. */
void
format_ipv6_addr(char *addr_str, const struct in6_addr *addr)
{
    inet_ntop(AF_INET6, addr, addr_str, INET6_ADDRSTRLEN);
}

void
print_ipv6_addr(struct ds *string, const struct in6_addr *addr)
{
    char addr_str[INET6_ADDRSTRLEN];

    format_ipv6_addr(addr_str, addr);
    ds_put_format(string, "%s", addr_str);
}

struct in6_addr ipv6_addr_bitand(const struct in6_addr *a,
                                 const struct in6_addr *b)
{
    int i;
    struct in6_addr dst;

#ifdef s6_addr32
    for (i=0; i<4; i++) {
        dst.s6_addr32[i] = a->s6_addr32[i] & b->s6_addr32[i];
    }
#else
    for (i=0; i<16; i++) {
        dst.s6_addr[i] = a->s6_addr[i] & b->s6_addr[i];
    }
#endif

    return dst;
}

/* Returns an in6_addr consisting of 'mask' high-order 1-bits and 128-N
 * low-order 0-bits. */
struct in6_addr
ipv6_create_mask(int mask)
{
    struct in6_addr netmask;
    uint8_t *netmaskp = &netmask.s6_addr[0];

    memset(&netmask, 0, sizeof netmask);
    while (mask > 8) {
        *netmaskp = 0xff;
        netmaskp++;
        mask -= 8;
    }

    if (mask) {
        *netmaskp = 0xff << (8 - mask);
    }

    return netmask;
}

/* Given the IPv6 netmask 'netmask', returns the number of bits of the
 * IPv6 address that it wildcards.  'netmask' must be a CIDR netmask (see
 * ipv6_is_cidr()). */
int
ipv6_count_cidr_bits(const struct in6_addr *netmask)
{
    int i;
    int count = 0;
    const uint8_t *netmaskp = &netmask->s6_addr[0];

    assert(ipv6_is_cidr(netmask));

    for (i=0; i<16; i++) {
        if (netmaskp[i] == 0xff) {
            count += 8;
        } else {
            uint8_t nm;

            for(nm = netmaskp[i]; nm; nm <<= 1) {
                count++;
            }
            break;
        }

    }

    return count;
}


/* Returns true if 'netmask' is a CIDR netmask, that is, if it consists of N
 * high-order 1-bits and 128-N low-order 0-bits. */
bool
ipv6_is_cidr(const struct in6_addr *netmask)
{
    const uint8_t *netmaskp = &netmask->s6_addr[0];
    int i;

    for (i=0; i<16; i++) {
        if (netmaskp[i] != 0xff) {
            uint8_t x = ~netmaskp[i];
            if (x & (x + 1)) {
                return false;
            }
            while (++i < 16) {
                if (netmaskp[i]) {
                    return false;
                }
            }
        }
    }

    return true;
}

/* Populates 'b' with a LACP packet containing 'pdu' with source address
 * 'eth_src'. */
void
compose_lacp_packet(struct ofpbuf *b, const uint8_t eth_src[ETH_ADDR_LEN],
                    const struct lacp_pdu *pdu)
{
    struct eth_header *eth;
    struct lacp_pdu *eth_pdu;

    ofpbuf_clear(b);

    ofpbuf_prealloc_tailroom(b, ETH_HEADER_LEN + LACP_PDU_LEN);
    eth = ofpbuf_put_zeros(b, ETH_HEADER_LEN);
    eth_pdu = ofpbuf_put(b, pdu, LACP_PDU_LEN);

    memcpy(eth->eth_dst, eth_addr_lacp, ETH_ADDR_LEN);
    memcpy(eth->eth_src, eth_src, ETH_ADDR_LEN);
    eth->eth_type = htons(ETH_TYPE_LACP);
}

/* Populates 'pdu' with a LACP PDU comprised of 'actor' and 'partner'. */
void
compose_lacp_pdu(const struct lacp_info *actor,
                 const struct lacp_info *partner, struct lacp_pdu *pdu)
{
    memset(pdu, 0, sizeof *pdu);

    pdu->subtype = 1;
    pdu->version = 1;

    pdu->actor_type = 1;
    pdu->actor_len = 20;
    pdu->actor = *actor;

    pdu->partner_type = 2;
    pdu->partner_len = 20;
    pdu->partner = *partner;

    pdu->collector_type = 3;
    pdu->collector_len = 16;
    pdu->collector_delay = htons(0);
}

/* Parses 'b' which represents a packet containing a LACP PDU.  This function
 * returns NULL if 'b' is malformed, or does not represent a LACP PDU format
 * supported by OVS.  Otherwise, it returns a pointer to the lacp_pdu contained
 * within 'b'. */
const struct lacp_pdu *
parse_lacp_packet(const struct ofpbuf *b)
{
    const struct lacp_pdu *pdu;

    pdu = ofpbuf_at(b, (uint8_t *)b->l3 - (uint8_t *)b->data, LACP_PDU_LEN);

    if (pdu && pdu->subtype == 1
        && pdu->actor_type == 1 && pdu->actor_len == 20
        && pdu->partner_type == 2 && pdu->partner_len == 20) {
        return pdu;
    } else {
        return NULL;
    }
}