bird/proto/ospf/packet.c

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/*
* BIRD -- OSPF
*
* (c) 1999--2005 Ondrej Filip <feela@network.cz>
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* (c) 2009--2014 Ondrej Zajicek <santiago@crfreenet.org>
* (c) 2009--2014 CZ.NIC z.s.p.o.
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "ospf.h"
#include "nest/password.h"
#include "lib/md5.h"
#include "lib/mac.h"
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#include "lib/socket.h"
void
ospf_pkt_fill_hdr(struct ospf_iface *ifa, void *buf, u8 h_type)
{
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struct ospf_proto *p = ifa->oa->po;
struct ospf_packet *pkt;
pkt = (struct ospf_packet *) buf;
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pkt->version = ospf_get_version(p);
pkt->type = h_type;
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pkt->length = htons(ospf_pkt_maxsize(ifa));
pkt->routerid = htonl(p->router_id);
pkt->areaid = htonl(ifa->oa->areaid);
pkt->checksum = 0;
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pkt->instance_id = ifa->instance_id;
pkt->autype = ifa->autype;
}
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uint
ospf_pkt_maxsize(struct ospf_iface *ifa)
{
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uint headers = SIZE_OF_IP_HEADER;
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/* Relevant just for OSPFv2 */
if (ifa->autype == OSPF_AUTH_CRYPT)
headers += OSPF_AUTH_CRYPT_SIZE;
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return ifa->tx_length - headers;
}
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/* We assume OSPFv2 in ospf_pkt_finalize() */
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static void
ospf_pkt_finalize(struct ospf_iface *ifa, struct ospf_packet *pkt)
{
struct password_item *passwd = NULL;
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union ospf_auth *auth = (void *) (pkt + 1);
uint plen = ntohs(pkt->length);
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pkt->checksum = 0;
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pkt->autype = ifa->autype;
bzero(auth, sizeof(union ospf_auth));
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/* Compatibility note: auth may contain anything if autype is
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none, but nonzero values do not work with Mikrotik OSPF */
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switch (ifa->autype)
{
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case OSPF_AUTH_SIMPLE:
passwd = password_find(ifa->passwords, 1);
if (!passwd)
{
log(L_ERR "No suitable password found for authentication");
return;
}
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strncpy(auth->password, passwd->password, sizeof(auth->password));
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case OSPF_AUTH_NONE:
{
void *body = (void *) (auth + 1);
uint blen = plen - sizeof(struct ospf_packet) - sizeof(union ospf_auth);
pkt->checksum = ipsum_calculate(pkt, sizeof(struct ospf_packet), body, blen, NULL);
}
break;
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case OSPF_AUTH_CRYPT:
passwd = password_find(ifa->passwords, 0);
if (!passwd)
{
log(L_ERR "No suitable password found for authentication");
return;
}
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/* Perhaps use random value to prevent replay attacks after
reboot when system does not have independent RTC? */
if (!ifa->csn)
{
ifa->csn = (u32) now;
ifa->csn_use = now;
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}
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/* We must have sufficient delay between sending a packet and increasing
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CSN to prevent reordering of packets (in a network) with different CSNs */
if ((now - ifa->csn_use) > 1)
ifa->csn++;
ifa->csn_use = now;
auth->md5.zero = 0;
auth->md5.keyid = passwd->id;
auth->md5.len = OSPF_AUTH_CRYPT_SIZE;
auth->md5.csn = htonl(ifa->csn);
void *tail = ((void *) pkt) + plen;
char password[OSPF_AUTH_CRYPT_SIZE];
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strncpy(password, passwd->password, sizeof(password));
struct hash_context ctx;
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md5_init(&ctx);
md5_update(&ctx, (char *) pkt, plen);
md5_update(&ctx, password, OSPF_AUTH_CRYPT_SIZE);
memcpy((byte *) tail, md5_final(&ctx), MD5_SIZE);
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break;
default:
bug("Unknown authentication type");
}
}
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/* We assume OSPFv2 in ospf_pkt_checkauth() */
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static int
ospf_pkt_checkauth(struct ospf_neighbor *n, struct ospf_iface *ifa, struct ospf_packet *pkt, uint len)
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{
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struct ospf_proto *p = ifa->oa->po;
union ospf_auth *auth = (void *) (pkt + 1);
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struct password_item *pass = NULL;
const char *err_dsc = NULL;
uint err_val = 0;
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uint plen = ntohs(pkt->length);
u8 autype = pkt->autype;
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if (autype != ifa->autype)
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DROP("authentication method mismatch", autype);
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switch (autype)
{
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case OSPF_AUTH_NONE:
return 1;
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case OSPF_AUTH_SIMPLE:
pass = password_find(ifa->passwords, 1);
if (!pass)
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DROP1("no password found");
if (!password_verify(pass, auth->password, sizeof(auth->password)))
DROP("wrong password", pass->id);
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return 1;
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case OSPF_AUTH_CRYPT:
if (auth->md5.len != OSPF_AUTH_CRYPT_SIZE)
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DROP("invalid MD5 digest length", auth->md5.len);
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if (plen + OSPF_AUTH_CRYPT_SIZE > len)
DROP("length mismatch", len);
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u32 rcv_csn = ntohl(auth->md5.csn);
if (n && (rcv_csn < n->csn))
// DROP("lower sequence number", rcv_csn);
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{
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/* We want to report both new and old CSN */
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - "
"lower sequence number (rcv %u, old %u)",
n->rid, ifa->ifname, rcv_csn, n->csn);
return 0;
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}
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pass = password_find_by_id(ifa->passwords, auth->md5.keyid);
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if (!pass)
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DROP("no suitable password found", auth->md5.keyid);
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byte *tail = ((byte *) pkt) + plen;
char received[OSPF_AUTH_CRYPT_SIZE];
memcpy(received, tail, OSPF_AUTH_CRYPT_SIZE);
strncpy(tail, pass->password, OSPF_AUTH_CRYPT_SIZE);
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struct hash_context ctx;
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md5_init(&ctx);
md5_update(&ctx, (byte *) pkt, plen + OSPF_AUTH_CRYPT_SIZE);
char *computed = md5_final(&ctx);
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if (memcmp(received, computed, OSPF_AUTH_CRYPT_SIZE))
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DROP("wrong MD5 digest", pass->id);
if (n)
n->csn = rcv_csn;
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return 1;
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default:
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bug("Unknown authentication type");
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}
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drop:
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - %s (%u)",
(n ? n->rid : ntohl(pkt->routerid)), ifa->ifname, err_dsc, err_val);
return 0;
}
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/**
* ospf_rx_hook
* @sk: socket we received the packet.
* @len: size of the packet
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*
* This is the entry point for messages from neighbors. Many checks (like
* authentication, checksums, size) are done before the packet is passed to
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* non generic functions.
*/
int
ospf_rx_hook(sock *sk, uint len)
{
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/* We want just packets from sk->iface. Unfortunately, on BSD we cannot filter
out other packets at kernel level and we receive all packets on all sockets */
if (sk->lifindex != sk->iface->index)
return 1;
DBG("OSPF: RX hook called (iface %s, src %I, dst %I)\n",
sk->iface->name, sk->faddr, sk->laddr);
/* Initially, the packet is associated with the 'master' iface */
struct ospf_iface *ifa = sk->data;
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struct ospf_proto *p = ifa->oa->po;
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const char *err_dsc = NULL;
uint err_val = 0;
/* Should not happen */
if (ifa->state <= OSPF_IS_LOOP)
return 1;
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int src_local, dst_local, dst_mcast;
src_local = ipa_in_net(sk->faddr, ifa->addr->prefix, ifa->addr->pxlen);
dst_local = ipa_equal(sk->laddr, ifa->addr->ip);
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dst_mcast = ipa_equal(sk->laddr, ifa->all_routers) || ipa_equal(sk->laddr, ifa->des_routers);
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if (ospf_is_v2(p))
{
/* First, we eliminate packets with strange address combinations.
* In OSPFv2, they might be for other ospf_ifaces (with different IP
* prefix) on the same real iface, so we don't log it. We enforce
* that (src_local || dst_local), therefore we are eliminating all
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* such cases.
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*/
if (dst_mcast && !src_local)
return 1;
if (!dst_mcast && !dst_local)
return 1;
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/* Ignore my own broadcast packets */
if (ifa->cf->real_bcast && ipa_equal(sk->faddr, ifa->addr->ip))
return 1;
}
else
{
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/* In OSPFv3, src_local and dst_local mean link-local.
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* RFC 5340 says that local (non-vlink) packets use
* link-local src address, but does not enforce it. Strange.
*/
if (dst_mcast && !src_local)
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LOG_PKT_WARN("Multicast packet received from non-link-local %I via %s",
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sk->faddr, ifa->ifname);
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}
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/* Second, we check packet length, checksum, and the protocol version */
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struct ospf_packet *pkt = (void *) sk_rx_buffer(sk, &len);
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if (pkt == NULL)
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DROP("bad IP header", len);
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if (ifa->check_ttl && (sk->rcv_ttl < 255))
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DROP("wrong TTL", sk->rcv_ttl);
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if (len < sizeof(struct ospf_packet))
DROP("too short", len);
if (pkt->version != ospf_get_version(p))
DROP("version mismatch", pkt->version);
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uint plen = ntohs(pkt->length);
if ((plen < sizeof(struct ospf_packet)) || ((plen % 4) != 0))
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DROP("invalid length", plen);
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if (sk->flags & SKF_TRUNCATED)
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{
/* If we have dynamic buffers and received truncated message, we expand RX buffer */
uint bs = plen + 256;
bs = BIRD_ALIGN(bs, 1024);
if (!ifa->cf->rx_buffer && (bs > sk->rbsize))
sk_set_rbsize(sk, bs);
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DROP("truncated", plen);
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}
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if (plen > len)
DROP("length mismatch", plen);
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if (ospf_is_v2(p) && (pkt->autype != OSPF_AUTH_CRYPT))
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{
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uint hlen = sizeof(struct ospf_packet) + sizeof(union ospf_auth);
uint blen = plen - hlen;
void *body = ((void *) pkt) + hlen;
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if (!ipsum_verify(pkt, sizeof(struct ospf_packet), body, blen, NULL))
DROP1("invalid checksum");
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}
/* Third, we resolve associated iface and handle vlinks. */
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u32 areaid = ntohl(pkt->areaid);
u32 rid = ntohl(pkt->routerid);
u8 instance_id = pkt->instance_id;
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if (areaid == ifa->oa->areaid)
{
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/* Matching area ID */
if (instance_id != ifa->instance_id)
return 1;
/* It is real iface, source should be local (in OSPFv2) */
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if (ospf_is_v2(p) && !src_local)
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DROP1("strange source address");
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goto found;
}
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else if ((areaid == 0) && !dst_mcast)
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{
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/* Backbone area ID and possible vlink packet */
if ((p->areano == 1) || !oa_is_ext(ifa->oa))
return 1;
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struct ospf_iface *iff = NULL;
WALK_LIST(iff, p->iface_list)
{
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if ((iff->type == OSPF_IT_VLINK) &&
(iff->voa == ifa->oa) &&
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(iff->instance_id == instance_id) &&
(iff->vid == rid))
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{
/* Vlink should be UP */
if (iff->state != OSPF_IS_PTP)
return 1;
ifa = iff;
goto found;
}
}
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/*
* Cannot find matching vlink. It is either misconfigured vlink; NBMA or
* PtMP with misconfigured area ID, or packet for some other instance (that
* is possible even if instance_id == ifa->instance_id, because it may be
* also vlink packet in the other instance, which is different namespace).
*/
return 1;
}
else
{
/* Non-matching area ID but cannot be vlink packet */
if (instance_id != ifa->instance_id)
return 1;
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DROP("area mismatch", areaid);
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}
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found:
if (ifa->stub) /* This shouldn't happen */
return 1;
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if (ipa_equal(sk->laddr, ifa->des_routers) && (ifa->sk_dr == 0))
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return 1;
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if (rid == p->router_id)
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DROP1("my own router ID");
if (rid == 0)
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DROP1("zero router ID");
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/* In OSPFv2, neighbors are identified by either IP or Router ID, based on network type */
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uint t = ifa->type;
struct ospf_neighbor *n;
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if (ospf_is_v2(p) && ((t == OSPF_IT_BCAST) || (t == OSPF_IT_NBMA) || (t == OSPF_IT_PTMP)))
n = find_neigh_by_ip(ifa, sk->faddr);
else
n = find_neigh(ifa, rid);
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if (!n && (pkt->type != HELLO_P))
{
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OSPF_TRACE(D_PACKETS, "Non-HELLO packet received from unknown nbr %R on %s, src %I",
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rid, ifa->ifname, sk->faddr);
return 1;
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}
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/* ospf_pkt_checkauth() has its own error logging */
if (ospf_is_v2(p) && !ospf_pkt_checkauth(n, ifa, pkt, len))
return 1;
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switch (pkt->type)
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{
case HELLO_P:
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ospf_receive_hello(pkt, ifa, n, sk->faddr);
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break;
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case DBDES_P:
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ospf_receive_dbdes(pkt, ifa, n);
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break;
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case LSREQ_P:
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ospf_receive_lsreq(pkt, ifa, n);
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break;
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case LSUPD_P:
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ospf_receive_lsupd(pkt, ifa, n);
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break;
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case LSACK_P:
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ospf_receive_lsack(pkt, ifa, n);
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break;
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default:
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DROP("invalid packet type", pkt->type);
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};
return 1;
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drop:
LOG_PKT("Bad packet from %I via %s - %s (%u)",
sk->faddr, ifa->ifname, err_dsc, err_val);
return 1;
}
/*
void
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ospf_tx_hook(sock * sk)
{
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struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);
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// struct proto *p = (struct proto *) (ifa->oa->p);
log(L_ERR "OSPF: TX hook called on %s", ifa->ifname);
}
*/
void
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ospf_err_hook(sock * sk, int err)
{
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struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);
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struct ospf_proto *p = ifa->oa->po;
log(L_ERR "%s: Socket error on %s: %M", p->p.name, ifa->ifname, err);
}
void
ospf_verr_hook(sock *sk, int err)
{
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struct ospf_proto *p = (struct ospf_proto *) (sk->data);
log(L_ERR "%s: Vlink socket error: %M", p->p.name, err);
}
void
ospf_send_to(struct ospf_iface *ifa, ip_addr dst)
{
sock *sk = ifa->sk;
struct ospf_packet *pkt = (struct ospf_packet *) sk->tbuf;
int plen = ntohs(pkt->length);
if (ospf_is_v2(ifa->oa->po))
{
if (ifa->autype == OSPF_AUTH_CRYPT)
plen += OSPF_AUTH_CRYPT_SIZE;
ospf_pkt_finalize(ifa, pkt);
}
int done = sk_send_to(sk, plen, dst, 0);
if (!done)
log(L_WARN "OSPF: TX queue full on %s", ifa->ifname);
}
void
ospf_send_to_agt(struct ospf_iface *ifa, u8 state)
{
struct ospf_neighbor *n;
WALK_LIST(n, ifa->neigh_list)
if (n->state >= state)
ospf_send_to(ifa, n->ip);
}
void
ospf_send_to_bdr(struct ospf_iface *ifa)
{
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if (ipa_nonzero(ifa->drip))
ospf_send_to(ifa, ifa->drip);
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if (ipa_nonzero(ifa->bdrip))
ospf_send_to(ifa, ifa->bdrip);
}