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freebsd-dev/sys/netinet/if_ether.c
Oleg Bulyzhin ff21796d25 Fix comment typo.
2017-08-09 10:46:34 +00:00

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/*-
* Copyright (c) 1982, 1986, 1988, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)if_ether.c 8.1 (Berkeley) 6/10/93
*/
/*
* Ethernet address resolution protocol.
* TODO:
* add "inuse/lock" bit (or ref. count) along with valid bit
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/rmlock.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/netisr.h>
#include <net/ethernet.h>
#include <net/route.h>
#include <net/vnet.h>
#include <netinet/in.h>
#include <netinet/in_fib.h>
#include <netinet/in_var.h>
#include <net/if_llatbl.h>
#include <netinet/if_ether.h>
#ifdef INET
#include <netinet/ip_carp.h>
#endif
#include <security/mac/mac_framework.h>
#define SIN(s) ((const struct sockaddr_in *)(s))
static struct timeval arp_lastlog;
static int arp_curpps;
static int arp_maxpps = 1;
/* Simple ARP state machine */
enum arp_llinfo_state {
ARP_LLINFO_INCOMPLETE = 0, /* No LLE data */
ARP_LLINFO_REACHABLE, /* LLE is valid */
ARP_LLINFO_VERIFY, /* LLE is valid, need refresh */
ARP_LLINFO_DELETED, /* LLE is deleted */
};
SYSCTL_DECL(_net_link_ether);
static SYSCTL_NODE(_net_link_ether, PF_INET, inet, CTLFLAG_RW, 0, "");
static SYSCTL_NODE(_net_link_ether, PF_ARP, arp, CTLFLAG_RW, 0, "");
/* timer values */
static VNET_DEFINE(int, arpt_keep) = (20*60); /* once resolved, good for 20
* minutes */
static VNET_DEFINE(int, arp_maxtries) = 5;
static VNET_DEFINE(int, arp_proxyall) = 0;
static VNET_DEFINE(int, arpt_down) = 20; /* keep incomplete entries for
* 20 seconds */
static VNET_DEFINE(int, arpt_rexmit) = 1; /* retransmit arp entries, sec*/
VNET_PCPUSTAT_DEFINE(struct arpstat, arpstat); /* ARP statistics, see if_arp.h */
VNET_PCPUSTAT_SYSINIT(arpstat);
#ifdef VIMAGE
VNET_PCPUSTAT_SYSUNINIT(arpstat);
#endif /* VIMAGE */
static VNET_DEFINE(int, arp_maxhold) = 1;
#define V_arpt_keep VNET(arpt_keep)
#define V_arpt_down VNET(arpt_down)
#define V_arpt_rexmit VNET(arpt_rexmit)
#define V_arp_maxtries VNET(arp_maxtries)
#define V_arp_proxyall VNET(arp_proxyall)
#define V_arp_maxhold VNET(arp_maxhold)
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, max_age, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(arpt_keep), 0,
"ARP entry lifetime in seconds");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, maxtries, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(arp_maxtries), 0,
"ARP resolution attempts before returning error");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, proxyall, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(arp_proxyall), 0,
"Enable proxy ARP for all suitable requests");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, wait, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(arpt_down), 0,
"Incomplete ARP entry lifetime in seconds");
SYSCTL_VNET_PCPUSTAT(_net_link_ether_arp, OID_AUTO, stats, struct arpstat,
arpstat, "ARP statistics (struct arpstat, net/if_arp.h)");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, maxhold, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(arp_maxhold), 0,
"Number of packets to hold per ARP entry");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, max_log_per_second,
CTLFLAG_RW, &arp_maxpps, 0,
"Maximum number of remotely triggered ARP messages that can be "
"logged per second");
/*
* Due to the exponential backoff algorithm used for the interval between GARP
* retransmissions, the maximum number of retransmissions is limited for
* sanity. This limit corresponds to a maximum interval between retransmissions
* of 2^16 seconds ~= 18 hours.
*
* Making this limit more dynamic is more complicated than worthwhile,
* especially since sending out GARPs spaced days apart would be of little
* use. A maximum dynamic limit would look something like:
*
* const int max = fls(INT_MAX / hz) - 1;
*/
#define MAX_GARP_RETRANSMITS 16
static int sysctl_garp_rexmit(SYSCTL_HANDLER_ARGS);
static int garp_rexmit_count = 0; /* GARP retransmission setting. */
SYSCTL_PROC(_net_link_ether_inet, OID_AUTO, garp_rexmit_count,
CTLTYPE_INT|CTLFLAG_RW|CTLFLAG_MPSAFE,
&garp_rexmit_count, 0, sysctl_garp_rexmit, "I",
"Number of times to retransmit GARP packets;"
" 0 to disable, maximum of 16");
#define ARP_LOG(pri, ...) do { \
if (ppsratecheck(&arp_lastlog, &arp_curpps, arp_maxpps)) \
log((pri), "arp: " __VA_ARGS__); \
} while (0)
static void arpintr(struct mbuf *);
static void arptimer(void *);
#ifdef INET
static void in_arpinput(struct mbuf *);
#endif
static void arp_check_update_lle(struct arphdr *ah, struct in_addr isaddr,
struct ifnet *ifp, int bridged, struct llentry *la);
static void arp_mark_lle_reachable(struct llentry *la);
static void arp_iflladdr(void *arg __unused, struct ifnet *ifp);
static eventhandler_tag iflladdr_tag;
static const struct netisr_handler arp_nh = {
.nh_name = "arp",
.nh_handler = arpintr,
.nh_proto = NETISR_ARP,
.nh_policy = NETISR_POLICY_SOURCE,
};
/*
* Timeout routine. Age arp_tab entries periodically.
*/
static void
arptimer(void *arg)
{
struct llentry *lle = (struct llentry *)arg;
struct ifnet *ifp;
int r_skip_req;
if (lle->la_flags & LLE_STATIC) {
return;
}
LLE_WLOCK(lle);
if (callout_pending(&lle->lle_timer)) {
/*
* Here we are a bit odd here in the treatment of
* active/pending. If the pending bit is set, it got
* rescheduled before I ran. The active
* bit we ignore, since if it was stopped
* in ll_tablefree() and was currently running
* it would have return 0 so the code would
* not have deleted it since the callout could
* not be stopped so we want to go through
* with the delete here now. If the callout
* was restarted, the pending bit will be back on and
* we just want to bail since the callout_reset would
* return 1 and our reference would have been removed
* by arpresolve() below.
*/
LLE_WUNLOCK(lle);
return;
}
ifp = lle->lle_tbl->llt_ifp;
CURVNET_SET(ifp->if_vnet);
switch (lle->ln_state) {
case ARP_LLINFO_REACHABLE:
/*
* Expiration time is approaching.
* Let's try to refresh entry if it is still
* in use.
*
* Set r_skip_req to get feedback from
* fast path. Change state and re-schedule
* ourselves.
*/
LLE_REQ_LOCK(lle);
lle->r_skip_req = 1;
LLE_REQ_UNLOCK(lle);
lle->ln_state = ARP_LLINFO_VERIFY;
callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
LLE_WUNLOCK(lle);
CURVNET_RESTORE();
return;
case ARP_LLINFO_VERIFY:
LLE_REQ_LOCK(lle);
r_skip_req = lle->r_skip_req;
LLE_REQ_UNLOCK(lle);
if (r_skip_req == 0 && lle->la_preempt > 0) {
/* Entry was used, issue refresh request */
struct in_addr dst;
dst = lle->r_l3addr.addr4;
lle->la_preempt--;
callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
LLE_WUNLOCK(lle);
arprequest(ifp, NULL, &dst, NULL);
CURVNET_RESTORE();
return;
}
/* Nothing happened. Reschedule if not too late */
if (lle->la_expire > time_uptime) {
callout_schedule(&lle->lle_timer, hz * V_arpt_rexmit);
LLE_WUNLOCK(lle);
CURVNET_RESTORE();
return;
}
break;
case ARP_LLINFO_INCOMPLETE:
case ARP_LLINFO_DELETED:
break;
}
if ((lle->la_flags & LLE_DELETED) == 0) {
int evt;
if (lle->la_flags & LLE_VALID)
evt = LLENTRY_EXPIRED;
else
evt = LLENTRY_TIMEDOUT;
EVENTHANDLER_INVOKE(lle_event, lle, evt);
}
callout_stop(&lle->lle_timer);
/* XXX: LOR avoidance. We still have ref on lle. */
LLE_WUNLOCK(lle);
IF_AFDATA_LOCK(ifp);
LLE_WLOCK(lle);
/* Guard against race with other llentry_free(). */
if (lle->la_flags & LLE_LINKED) {
LLE_REMREF(lle);
lltable_unlink_entry(lle->lle_tbl, lle);
}
IF_AFDATA_UNLOCK(ifp);
size_t pkts_dropped = llentry_free(lle);
ARPSTAT_ADD(dropped, pkts_dropped);
ARPSTAT_INC(timeouts);
CURVNET_RESTORE();
}
/*
* Stores link-layer header for @ifp in format suitable for if_output()
* into buffer @buf. Resulting header length is stored in @bufsize.
*
* Returns 0 on success.
*/
static int
arp_fillheader(struct ifnet *ifp, struct arphdr *ah, int bcast, u_char *buf,
size_t *bufsize)
{
struct if_encap_req ereq;
int error;
bzero(buf, *bufsize);
bzero(&ereq, sizeof(ereq));
ereq.buf = buf;
ereq.bufsize = *bufsize;
ereq.rtype = IFENCAP_LL;
ereq.family = AF_ARP;
ereq.lladdr = ar_tha(ah);
ereq.hdata = (u_char *)ah;
if (bcast)
ereq.flags = IFENCAP_FLAG_BROADCAST;
error = ifp->if_requestencap(ifp, &ereq);
if (error == 0)
*bufsize = ereq.bufsize;
return (error);
}
/*
* Broadcast an ARP request. Caller specifies:
* - arp header source ip address
* - arp header target ip address
* - arp header source ethernet address
*/
void
arprequest(struct ifnet *ifp, const struct in_addr *sip,
const struct in_addr *tip, u_char *enaddr)
{
struct mbuf *m;
struct arphdr *ah;
struct sockaddr sa;
u_char *carpaddr = NULL;
uint8_t linkhdr[LLE_MAX_LINKHDR];
size_t linkhdrsize;
struct route ro;
int error;
if (sip == NULL) {
/*
* The caller did not supply a source address, try to find
* a compatible one among those assigned to this interface.
*/
struct ifaddr *ifa;
IF_ADDR_RLOCK(ifp);
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
if (ifa->ifa_addr->sa_family != AF_INET)
continue;
if (ifa->ifa_carp) {
if ((*carp_iamatch_p)(ifa, &carpaddr) == 0)
continue;
sip = &IA_SIN(ifa)->sin_addr;
} else {
carpaddr = NULL;
sip = &IA_SIN(ifa)->sin_addr;
}
if (0 == ((sip->s_addr ^ tip->s_addr) &
IA_MASKSIN(ifa)->sin_addr.s_addr))
break; /* found it. */
}
IF_ADDR_RUNLOCK(ifp);
if (sip == NULL) {
printf("%s: cannot find matching address\n", __func__);
return;
}
}
if (enaddr == NULL)
enaddr = carpaddr ? carpaddr : (u_char *)IF_LLADDR(ifp);
if ((m = m_gethdr(M_NOWAIT, MT_DATA)) == NULL)
return;
m->m_len = sizeof(*ah) + 2 * sizeof(struct in_addr) +
2 * ifp->if_addrlen;
m->m_pkthdr.len = m->m_len;
M_ALIGN(m, m->m_len);
ah = mtod(m, struct arphdr *);
bzero((caddr_t)ah, m->m_len);
#ifdef MAC
mac_netinet_arp_send(ifp, m);
#endif
ah->ar_pro = htons(ETHERTYPE_IP);
ah->ar_hln = ifp->if_addrlen; /* hardware address length */
ah->ar_pln = sizeof(struct in_addr); /* protocol address length */
ah->ar_op = htons(ARPOP_REQUEST);
bcopy(enaddr, ar_sha(ah), ah->ar_hln);
bcopy(sip, ar_spa(ah), ah->ar_pln);
bcopy(tip, ar_tpa(ah), ah->ar_pln);
sa.sa_family = AF_ARP;
sa.sa_len = 2;
/* Calculate link header for sending frame */
bzero(&ro, sizeof(ro));
linkhdrsize = sizeof(linkhdr);
error = arp_fillheader(ifp, ah, 1, linkhdr, &linkhdrsize);
if (error != 0 && error != EAFNOSUPPORT) {
ARP_LOG(LOG_ERR, "Failed to calculate ARP header on %s: %d\n",
if_name(ifp), error);
return;
}
ro.ro_prepend = linkhdr;
ro.ro_plen = linkhdrsize;
ro.ro_flags = 0;
m->m_flags |= M_BCAST;
m_clrprotoflags(m); /* Avoid confusing lower layers. */
(*ifp->if_output)(ifp, m, &sa, &ro);
ARPSTAT_INC(txrequests);
}
/*
* Resolve an IP address into an ethernet address - heavy version.
* Used internally by arpresolve().
* We have already checked than we can't use existing lle without
* modification so we have to acquire LLE_EXCLUSIVE lle lock.
*
* On success, desten and flags are filled in and the function returns 0;
* If the packet must be held pending resolution, we return EWOULDBLOCK
* On other errors, we return the corresponding error code.
* Note that m_freem() handles NULL.
*/
static int
arpresolve_full(struct ifnet *ifp, int is_gw, int flags, struct mbuf *m,
const struct sockaddr *dst, u_char *desten, uint32_t *pflags,
struct llentry **plle)
{
struct llentry *la = NULL, *la_tmp;
struct mbuf *curr = NULL;
struct mbuf *next = NULL;
int error, renew;
char *lladdr;
int ll_len;
if (pflags != NULL)
*pflags = 0;
if (plle != NULL)
*plle = NULL;
if ((flags & LLE_CREATE) == 0) {
IF_AFDATA_RLOCK(ifp);
la = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
IF_AFDATA_RUNLOCK(ifp);
}
if (la == NULL && (ifp->if_flags & (IFF_NOARP | IFF_STATICARP)) == 0) {
la = lltable_alloc_entry(LLTABLE(ifp), 0, dst);
if (la == NULL) {
char addrbuf[INET_ADDRSTRLEN];
log(LOG_DEBUG,
"arpresolve: can't allocate llinfo for %s on %s\n",
inet_ntoa_r(SIN(dst)->sin_addr, addrbuf),
if_name(ifp));
m_freem(m);
return (EINVAL);
}
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(la);
la_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
/* Prefer ANY existing lle over newly-created one */
if (la_tmp == NULL)
lltable_link_entry(LLTABLE(ifp), la);
IF_AFDATA_WUNLOCK(ifp);
if (la_tmp != NULL) {
lltable_free_entry(LLTABLE(ifp), la);
la = la_tmp;
}
}
if (la == NULL) {
m_freem(m);
return (EINVAL);
}
if ((la->la_flags & LLE_VALID) &&
((la->la_flags & LLE_STATIC) || la->la_expire > time_uptime)) {
if (flags & LLE_ADDRONLY) {
lladdr = la->ll_addr;
ll_len = ifp->if_addrlen;
} else {
lladdr = la->r_linkdata;
ll_len = la->r_hdrlen;
}
bcopy(lladdr, desten, ll_len);
/* Check if we have feedback request from arptimer() */
if (la->r_skip_req != 0) {
LLE_REQ_LOCK(la);
la->r_skip_req = 0; /* Notify that entry was used */
LLE_REQ_UNLOCK(la);
}
if (pflags != NULL)
*pflags = la->la_flags & (LLE_VALID|LLE_IFADDR);
if (plle) {
LLE_ADDREF(la);
*plle = la;
}
LLE_WUNLOCK(la);
return (0);
}
renew = (la->la_asked == 0 || la->la_expire != time_uptime);
/*
* There is an arptab entry, but no ethernet address
* response yet. Add the mbuf to the list, dropping
* the oldest packet if we have exceeded the system
* setting.
*/
if (m != NULL) {
if (la->la_numheld >= V_arp_maxhold) {
if (la->la_hold != NULL) {
next = la->la_hold->m_nextpkt;
m_freem(la->la_hold);
la->la_hold = next;
la->la_numheld--;
ARPSTAT_INC(dropped);
}
}
if (la->la_hold != NULL) {
curr = la->la_hold;
while (curr->m_nextpkt != NULL)
curr = curr->m_nextpkt;
curr->m_nextpkt = m;
} else
la->la_hold = m;
la->la_numheld++;
}
/*
* Return EWOULDBLOCK if we have tried less than arp_maxtries. It
* will be masked by ether_output(). Return EHOSTDOWN/EHOSTUNREACH
* if we have already sent arp_maxtries ARP requests. Retransmit the
* ARP request, but not faster than one request per second.
*/
if (la->la_asked < V_arp_maxtries)
error = EWOULDBLOCK; /* First request. */
else
error = is_gw != 0 ? EHOSTUNREACH : EHOSTDOWN;
if (renew) {
int canceled;
LLE_ADDREF(la);
la->la_expire = time_uptime;
canceled = callout_reset(&la->lle_timer, hz * V_arpt_down,
arptimer, la);
if (canceled)
LLE_REMREF(la);
la->la_asked++;
LLE_WUNLOCK(la);
arprequest(ifp, NULL, &SIN(dst)->sin_addr, NULL);
return (error);
}
LLE_WUNLOCK(la);
return (error);
}
/*
* Resolve an IP address into an ethernet address.
*/
int
arpresolve_addr(struct ifnet *ifp, int flags, const struct sockaddr *dst,
char *desten, uint32_t *pflags, struct llentry **plle)
{
int error;
flags |= LLE_ADDRONLY;
error = arpresolve_full(ifp, 0, flags, NULL, dst, desten, pflags, plle);
return (error);
}
/*
* Lookups link header based on an IP address.
* On input:
* ifp is the interface we use
* is_gw != 0 if @dst represents gateway to some destination
* m is the mbuf. May be NULL if we don't have a packet.
* dst is the next hop,
* desten is the storage to put LL header.
* flags returns subset of lle flags: LLE_VALID | LLE_IFADDR
*
* On success, full/partial link header and flags are filled in and
* the function returns 0.
* If the packet must be held pending resolution, we return EWOULDBLOCK
* On other errors, we return the corresponding error code.
* Note that m_freem() handles NULL.
*/
int
arpresolve(struct ifnet *ifp, int is_gw, struct mbuf *m,
const struct sockaddr *dst, u_char *desten, uint32_t *pflags,
struct llentry **plle)
{
struct llentry *la = NULL;
if (pflags != NULL)
*pflags = 0;
if (plle != NULL)
*plle = NULL;
if (m != NULL) {
if (m->m_flags & M_BCAST) {
/* broadcast */
(void)memcpy(desten,
ifp->if_broadcastaddr, ifp->if_addrlen);
return (0);
}
if (m->m_flags & M_MCAST) {
/* multicast */
ETHER_MAP_IP_MULTICAST(&SIN(dst)->sin_addr, desten);
return (0);
}
}
IF_AFDATA_RLOCK(ifp);
la = lla_lookup(LLTABLE(ifp), plle ? LLE_EXCLUSIVE : LLE_UNLOCKED, dst);
if (la != NULL && (la->r_flags & RLLE_VALID) != 0) {
/* Entry found, let's copy lle info */
bcopy(la->r_linkdata, desten, la->r_hdrlen);
if (pflags != NULL)
*pflags = LLE_VALID | (la->r_flags & RLLE_IFADDR);
/* Check if we have feedback request from arptimer() */
if (la->r_skip_req != 0) {
LLE_REQ_LOCK(la);
la->r_skip_req = 0; /* Notify that entry was used */
LLE_REQ_UNLOCK(la);
}
if (plle) {
LLE_ADDREF(la);
*plle = la;
LLE_WUNLOCK(la);
}
IF_AFDATA_RUNLOCK(ifp);
return (0);
}
if (plle && la)
LLE_WUNLOCK(la);
IF_AFDATA_RUNLOCK(ifp);
return (arpresolve_full(ifp, is_gw, la == NULL ? LLE_CREATE : 0, m, dst,
desten, pflags, plle));
}
/*
* Common length and type checks are done here,
* then the protocol-specific routine is called.
*/
static void
arpintr(struct mbuf *m)
{
struct arphdr *ar;
struct ifnet *ifp;
char *layer;
int hlen;
ifp = m->m_pkthdr.rcvif;
if (m->m_len < sizeof(struct arphdr) &&
((m = m_pullup(m, sizeof(struct arphdr))) == NULL)) {
ARP_LOG(LOG_NOTICE, "packet with short header received on %s\n",
if_name(ifp));
return;
}
ar = mtod(m, struct arphdr *);
/* Check if length is sufficient */
if (m->m_len < arphdr_len(ar)) {
m = m_pullup(m, arphdr_len(ar));
if (m == NULL) {
ARP_LOG(LOG_NOTICE, "short packet received on %s\n",
if_name(ifp));
return;
}
ar = mtod(m, struct arphdr *);
}
hlen = 0;
layer = "";
switch (ntohs(ar->ar_hrd)) {
case ARPHRD_ETHER:
hlen = ETHER_ADDR_LEN; /* RFC 826 */
layer = "ethernet";
break;
case ARPHRD_IEEE802:
hlen = 6; /* RFC 1390, FDDI_ADDR_LEN */
layer = "fddi";
break;
case ARPHRD_ARCNET:
hlen = 1; /* RFC 1201, ARC_ADDR_LEN */
layer = "arcnet";
break;
case ARPHRD_INFINIBAND:
hlen = 20; /* RFC 4391, INFINIBAND_ALEN */
layer = "infiniband";
break;
case ARPHRD_IEEE1394:
hlen = 0; /* SHALL be 16 */ /* RFC 2734 */
layer = "firewire";
/*
* Restrict too long hardware addresses.
* Currently we are capable of handling 20-byte
* addresses ( sizeof(lle->ll_addr) )
*/
if (ar->ar_hln >= 20)
hlen = 16;
break;
default:
ARP_LOG(LOG_NOTICE,
"packet with unknown hardware format 0x%02d received on "
"%s\n", ntohs(ar->ar_hrd), if_name(ifp));
m_freem(m);
return;
}
if (hlen != 0 && hlen != ar->ar_hln) {
ARP_LOG(LOG_NOTICE,
"packet with invalid %s address length %d received on %s\n",
layer, ar->ar_hln, if_name(ifp));
m_freem(m);
return;
}
ARPSTAT_INC(received);
switch (ntohs(ar->ar_pro)) {
#ifdef INET
case ETHERTYPE_IP:
in_arpinput(m);
return;
#endif
}
m_freem(m);
}
#ifdef INET
/*
* ARP for Internet protocols on 10 Mb/s Ethernet.
* Algorithm is that given in RFC 826.
* In addition, a sanity check is performed on the sender
* protocol address, to catch impersonators.
* We no longer handle negotiations for use of trailer protocol:
* Formerly, ARP replied for protocol type ETHERTYPE_TRAIL sent
* along with IP replies if we wanted trailers sent to us,
* and also sent them in response to IP replies.
* This allowed either end to announce the desire to receive
* trailer packets.
* We no longer reply to requests for ETHERTYPE_TRAIL protocol either,
* but formerly didn't normally send requests.
*/
static int log_arp_wrong_iface = 1;
static int log_arp_movements = 1;
static int log_arp_permanent_modify = 1;
static int allow_multicast = 0;
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_wrong_iface, CTLFLAG_RW,
&log_arp_wrong_iface, 0,
"log arp packets arriving on the wrong interface");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_movements, CTLFLAG_RW,
&log_arp_movements, 0,
"log arp replies from MACs different than the one in the cache");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, log_arp_permanent_modify, CTLFLAG_RW,
&log_arp_permanent_modify, 0,
"log arp replies from MACs different than the one in the permanent arp entry");
SYSCTL_INT(_net_link_ether_inet, OID_AUTO, allow_multicast, CTLFLAG_RW,
&allow_multicast, 0, "accept multicast addresses");
static void
in_arpinput(struct mbuf *m)
{
struct rm_priotracker in_ifa_tracker;
struct arphdr *ah;
struct ifnet *ifp = m->m_pkthdr.rcvif;
struct llentry *la = NULL, *la_tmp;
struct ifaddr *ifa;
struct in_ifaddr *ia;
struct sockaddr sa;
struct in_addr isaddr, itaddr, myaddr;
u_int8_t *enaddr = NULL;
int op;
int bridged = 0, is_bridge = 0;
int carped;
struct sockaddr_in sin;
struct sockaddr *dst;
struct nhop4_basic nh4;
uint8_t linkhdr[LLE_MAX_LINKHDR];
struct route ro;
size_t linkhdrsize;
int lladdr_off;
int error;
char addrbuf[INET_ADDRSTRLEN];
sin.sin_len = sizeof(struct sockaddr_in);
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = 0;
if (ifp->if_bridge)
bridged = 1;
if (ifp->if_type == IFT_BRIDGE)
is_bridge = 1;
/*
* We already have checked that mbuf contains enough contiguous data
* to hold entire arp message according to the arp header.
*/
ah = mtod(m, struct arphdr *);
/*
* ARP is only for IPv4 so we can reject packets with
* a protocol length not equal to an IPv4 address.
*/
if (ah->ar_pln != sizeof(struct in_addr)) {
ARP_LOG(LOG_NOTICE, "requested protocol length != %zu\n",
sizeof(struct in_addr));
goto drop;
}
if (allow_multicast == 0 && ETHER_IS_MULTICAST(ar_sha(ah))) {
ARP_LOG(LOG_NOTICE, "%*D is multicast\n",
ifp->if_addrlen, (u_char *)ar_sha(ah), ":");
goto drop;
}
op = ntohs(ah->ar_op);
(void)memcpy(&isaddr, ar_spa(ah), sizeof (isaddr));
(void)memcpy(&itaddr, ar_tpa(ah), sizeof (itaddr));
if (op == ARPOP_REPLY)
ARPSTAT_INC(rxreplies);
/*
* For a bridge, we want to check the address irrespective
* of the receive interface. (This will change slightly
* when we have clusters of interfaces).
*/
IN_IFADDR_RLOCK(&in_ifa_tracker);
LIST_FOREACH(ia, INADDR_HASH(itaddr.s_addr), ia_hash) {
if (((bridged && ia->ia_ifp->if_bridge == ifp->if_bridge) ||
ia->ia_ifp == ifp) &&
itaddr.s_addr == ia->ia_addr.sin_addr.s_addr &&
(ia->ia_ifa.ifa_carp == NULL ||
(*carp_iamatch_p)(&ia->ia_ifa, &enaddr))) {
ifa_ref(&ia->ia_ifa);
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
goto match;
}
}
LIST_FOREACH(ia, INADDR_HASH(isaddr.s_addr), ia_hash)
if (((bridged && ia->ia_ifp->if_bridge == ifp->if_bridge) ||
ia->ia_ifp == ifp) &&
isaddr.s_addr == ia->ia_addr.sin_addr.s_addr) {
ifa_ref(&ia->ia_ifa);
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
goto match;
}
#define BDG_MEMBER_MATCHES_ARP(addr, ifp, ia) \
(ia->ia_ifp->if_bridge == ifp->if_softc && \
!bcmp(IF_LLADDR(ia->ia_ifp), IF_LLADDR(ifp), ifp->if_addrlen) && \
addr == ia->ia_addr.sin_addr.s_addr)
/*
* Check the case when bridge shares its MAC address with
* some of its children, so packets are claimed by bridge
* itself (bridge_input() does it first), but they are really
* meant to be destined to the bridge member.
*/
if (is_bridge) {
LIST_FOREACH(ia, INADDR_HASH(itaddr.s_addr), ia_hash) {
if (BDG_MEMBER_MATCHES_ARP(itaddr.s_addr, ifp, ia)) {
ifa_ref(&ia->ia_ifa);
ifp = ia->ia_ifp;
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
goto match;
}
}
}
#undef BDG_MEMBER_MATCHES_ARP
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
/*
* No match, use the first inet address on the receive interface
* as a dummy address for the rest of the function.
*/
IF_ADDR_RLOCK(ifp);
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link)
if (ifa->ifa_addr->sa_family == AF_INET &&
(ifa->ifa_carp == NULL ||
(*carp_iamatch_p)(ifa, &enaddr))) {
ia = ifatoia(ifa);
ifa_ref(ifa);
IF_ADDR_RUNLOCK(ifp);
goto match;
}
IF_ADDR_RUNLOCK(ifp);
/*
* If bridging, fall back to using any inet address.
*/
IN_IFADDR_RLOCK(&in_ifa_tracker);
if (!bridged || (ia = TAILQ_FIRST(&V_in_ifaddrhead)) == NULL) {
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
goto drop;
}
ifa_ref(&ia->ia_ifa);
IN_IFADDR_RUNLOCK(&in_ifa_tracker);
match:
if (!enaddr)
enaddr = (u_int8_t *)IF_LLADDR(ifp);
carped = (ia->ia_ifa.ifa_carp != NULL);
myaddr = ia->ia_addr.sin_addr;
ifa_free(&ia->ia_ifa);
if (!bcmp(ar_sha(ah), enaddr, ifp->if_addrlen))
goto drop; /* it's from me, ignore it. */
if (!bcmp(ar_sha(ah), ifp->if_broadcastaddr, ifp->if_addrlen)) {
ARP_LOG(LOG_NOTICE, "link address is broadcast for IP address "
"%s!\n", inet_ntoa_r(isaddr, addrbuf));
goto drop;
}
if (ifp->if_addrlen != ah->ar_hln) {
ARP_LOG(LOG_WARNING, "from %*D: addr len: new %d, "
"i/f %d (ignored)\n", ifp->if_addrlen,
(u_char *) ar_sha(ah), ":", ah->ar_hln,
ifp->if_addrlen);
goto drop;
}
/*
* Warn if another host is using the same IP address, but only if the
* IP address isn't 0.0.0.0, which is used for DHCP only, in which
* case we suppress the warning to avoid false positive complaints of
* potential misconfiguration.
*/
if (!bridged && !carped && isaddr.s_addr == myaddr.s_addr &&
myaddr.s_addr != 0) {
ARP_LOG(LOG_ERR, "%*D is using my IP address %s on %s!\n",
ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
inet_ntoa_r(isaddr, addrbuf), ifp->if_xname);
itaddr = myaddr;
ARPSTAT_INC(dupips);
goto reply;
}
if (ifp->if_flags & IFF_STATICARP)
goto reply;
bzero(&sin, sizeof(sin));
sin.sin_len = sizeof(struct sockaddr_in);
sin.sin_family = AF_INET;
sin.sin_addr = isaddr;
dst = (struct sockaddr *)&sin;
IF_AFDATA_RLOCK(ifp);
la = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
IF_AFDATA_RUNLOCK(ifp);
if (la != NULL)
arp_check_update_lle(ah, isaddr, ifp, bridged, la);
else if (itaddr.s_addr == myaddr.s_addr) {
/*
* Request/reply to our address, but no lle exists yet.
* Calculate full link prepend to use in lle.
*/
linkhdrsize = sizeof(linkhdr);
if (lltable_calc_llheader(ifp, AF_INET, ar_sha(ah), linkhdr,
&linkhdrsize, &lladdr_off) != 0)
goto reply;
/* Allocate new entry */
la = lltable_alloc_entry(LLTABLE(ifp), 0, dst);
if (la == NULL) {
/*
* lle creation may fail if source address belongs
* to non-directly connected subnet. However, we
* will try to answer the request instead of dropping
* frame.
*/
goto reply;
}
lltable_set_entry_addr(ifp, la, linkhdr, linkhdrsize,
lladdr_off);
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(la);
la_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
/*
* Check if lle still does not exists.
* If it does, that means that we either
* 1) have configured it explicitly, via
* 1a) 'arp -s' static entry or
* 1b) interface address static record
* or
* 2) it was the result of sending first packet to-host
* or
* 3) it was another arp reply packet we handled in
* different thread.
*
* In all cases except 3) we definitely need to prefer
* existing lle. For the sake of simplicity, prefer any
* existing lle over newly-create one.
*/
if (la_tmp == NULL)
lltable_link_entry(LLTABLE(ifp), la);
IF_AFDATA_WUNLOCK(ifp);
if (la_tmp == NULL) {
arp_mark_lle_reachable(la);
LLE_WUNLOCK(la);
} else {
/* Free newly-create entry and handle packet */
lltable_free_entry(LLTABLE(ifp), la);
la = la_tmp;
la_tmp = NULL;
arp_check_update_lle(ah, isaddr, ifp, bridged, la);
/* arp_check_update_lle() returns @la unlocked */
}
la = NULL;
}
reply:
if (op != ARPOP_REQUEST)
goto drop;
ARPSTAT_INC(rxrequests);
if (itaddr.s_addr == myaddr.s_addr) {
/* Shortcut.. the receiving interface is the target. */
(void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
(void)memcpy(ar_sha(ah), enaddr, ah->ar_hln);
} else {
struct llentry *lle = NULL;
sin.sin_addr = itaddr;
IF_AFDATA_RLOCK(ifp);
lle = lla_lookup(LLTABLE(ifp), 0, (struct sockaddr *)&sin);
IF_AFDATA_RUNLOCK(ifp);
if ((lle != NULL) && (lle->la_flags & LLE_PUB)) {
(void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
(void)memcpy(ar_sha(ah), lle->ll_addr, ah->ar_hln);
LLE_RUNLOCK(lle);
} else {
if (lle != NULL)
LLE_RUNLOCK(lle);
if (!V_arp_proxyall)
goto drop;
/* XXX MRT use table 0 for arp reply */
if (fib4_lookup_nh_basic(0, itaddr, 0, 0, &nh4) != 0)
goto drop;
/*
* Don't send proxies for nodes on the same interface
* as this one came out of, or we'll get into a fight
* over who claims what Ether address.
*/
if (nh4.nh_ifp == ifp)
goto drop;
(void)memcpy(ar_tha(ah), ar_sha(ah), ah->ar_hln);
(void)memcpy(ar_sha(ah), enaddr, ah->ar_hln);
/*
* Also check that the node which sent the ARP packet
* is on the interface we expect it to be on. This
* avoids ARP chaos if an interface is connected to the
* wrong network.
*/
/* XXX MRT use table 0 for arp checks */
if (fib4_lookup_nh_basic(0, isaddr, 0, 0, &nh4) != 0)
goto drop;
if (nh4.nh_ifp != ifp) {
ARP_LOG(LOG_INFO, "proxy: ignoring request"
" from %s via %s\n",
inet_ntoa_r(isaddr, addrbuf),
ifp->if_xname);
goto drop;
}
#ifdef DEBUG_PROXY
printf("arp: proxying for %s\n",
inet_ntoa_r(itaddr, addrbuf));
#endif
}
}
if (itaddr.s_addr == myaddr.s_addr &&
IN_LINKLOCAL(ntohl(itaddr.s_addr))) {
/* RFC 3927 link-local IPv4; always reply by broadcast. */
#ifdef DEBUG_LINKLOCAL
printf("arp: sending reply for link-local addr %s\n",
inet_ntoa_r(itaddr, addrbuf));
#endif
m->m_flags |= M_BCAST;
m->m_flags &= ~M_MCAST;
} else {
/* default behaviour; never reply by broadcast. */
m->m_flags &= ~(M_BCAST|M_MCAST);
}
(void)memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
(void)memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
ah->ar_op = htons(ARPOP_REPLY);
ah->ar_pro = htons(ETHERTYPE_IP); /* let's be sure! */
m->m_len = sizeof(*ah) + (2 * ah->ar_pln) + (2 * ah->ar_hln);
m->m_pkthdr.len = m->m_len;
m->m_pkthdr.rcvif = NULL;
sa.sa_family = AF_ARP;
sa.sa_len = 2;
/* Calculate link header for sending frame */
bzero(&ro, sizeof(ro));
linkhdrsize = sizeof(linkhdr);
error = arp_fillheader(ifp, ah, 0, linkhdr, &linkhdrsize);
/*
* arp_fillheader() may fail due to lack of support inside encap request
* routing. This is not necessary an error, AF_ARP can/should be handled
* by if_output().
*/
if (error != 0 && error != EAFNOSUPPORT) {
ARP_LOG(LOG_ERR, "Failed to calculate ARP header on %s: %d\n",
if_name(ifp), error);
return;
}
ro.ro_prepend = linkhdr;
ro.ro_plen = linkhdrsize;
ro.ro_flags = 0;
m_clrprotoflags(m); /* Avoid confusing lower layers. */
(*ifp->if_output)(ifp, m, &sa, &ro);
ARPSTAT_INC(txreplies);
return;
drop:
m_freem(m);
}
#endif
/*
* Checks received arp data against existing @la.
* Updates lle state/performs notification if necessary.
*/
static void
arp_check_update_lle(struct arphdr *ah, struct in_addr isaddr, struct ifnet *ifp,
int bridged, struct llentry *la)
{
struct sockaddr sa;
struct mbuf *m_hold, *m_hold_next;
uint8_t linkhdr[LLE_MAX_LINKHDR];
size_t linkhdrsize;
int lladdr_off;
char addrbuf[INET_ADDRSTRLEN];
LLE_WLOCK_ASSERT(la);
/* the following is not an error when doing bridging */
if (!bridged && la->lle_tbl->llt_ifp != ifp) {
if (log_arp_wrong_iface)
ARP_LOG(LOG_WARNING, "%s is on %s "
"but got reply from %*D on %s\n",
inet_ntoa_r(isaddr, addrbuf),
la->lle_tbl->llt_ifp->if_xname,
ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
ifp->if_xname);
LLE_WUNLOCK(la);
return;
}
if ((la->la_flags & LLE_VALID) &&
bcmp(ar_sha(ah), la->ll_addr, ifp->if_addrlen)) {
if (la->la_flags & LLE_STATIC) {
LLE_WUNLOCK(la);
if (log_arp_permanent_modify)
ARP_LOG(LOG_ERR,
"%*D attempts to modify "
"permanent entry for %s on %s\n",
ifp->if_addrlen,
(u_char *)ar_sha(ah), ":",
inet_ntoa_r(isaddr, addrbuf),
ifp->if_xname);
return;
}
if (log_arp_movements) {
ARP_LOG(LOG_INFO, "%s moved from %*D "
"to %*D on %s\n",
inet_ntoa_r(isaddr, addrbuf),
ifp->if_addrlen,
(u_char *)la->ll_addr, ":",
ifp->if_addrlen, (u_char *)ar_sha(ah), ":",
ifp->if_xname);
}
}
/* Calculate full link prepend to use in lle */
linkhdrsize = sizeof(linkhdr);
if (lltable_calc_llheader(ifp, AF_INET, ar_sha(ah), linkhdr,
&linkhdrsize, &lladdr_off) != 0)
return;
/* Check if something has changed */
if (memcmp(la->r_linkdata, linkhdr, linkhdrsize) != 0 ||
(la->la_flags & LLE_VALID) == 0) {
/* Try to perform LLE update */
if (lltable_try_set_entry_addr(ifp, la, linkhdr, linkhdrsize,
lladdr_off) == 0)
return;
/* Clear fast path feedback request if set */
la->r_skip_req = 0;
}
arp_mark_lle_reachable(la);
/*
* The packets are all freed within the call to the output
* routine.
*
* NB: The lock MUST be released before the call to the
* output routine.
*/
if (la->la_hold != NULL) {
m_hold = la->la_hold;
la->la_hold = NULL;
la->la_numheld = 0;
lltable_fill_sa_entry(la, &sa);
LLE_WUNLOCK(la);
for (; m_hold != NULL; m_hold = m_hold_next) {
m_hold_next = m_hold->m_nextpkt;
m_hold->m_nextpkt = NULL;
/* Avoid confusing lower layers. */
m_clrprotoflags(m_hold);
(*ifp->if_output)(ifp, m_hold, &sa, NULL);
}
} else
LLE_WUNLOCK(la);
}
static void
arp_mark_lle_reachable(struct llentry *la)
{
int canceled, wtime;
LLE_WLOCK_ASSERT(la);
la->ln_state = ARP_LLINFO_REACHABLE;
EVENTHANDLER_INVOKE(lle_event, la, LLENTRY_RESOLVED);
if (!(la->la_flags & LLE_STATIC)) {
LLE_ADDREF(la);
la->la_expire = time_uptime + V_arpt_keep;
wtime = V_arpt_keep - V_arp_maxtries * V_arpt_rexmit;
if (wtime < 0)
wtime = V_arpt_keep;
canceled = callout_reset(&la->lle_timer,
hz * wtime, arptimer, la);
if (canceled)
LLE_REMREF(la);
}
la->la_asked = 0;
la->la_preempt = V_arp_maxtries;
}
/*
* Add permanent link-layer record for given interface address.
*/
static __noinline void
arp_add_ifa_lle(struct ifnet *ifp, const struct sockaddr *dst)
{
struct llentry *lle, *lle_tmp;
/*
* Interface address LLE record is considered static
* because kernel code relies on LLE_STATIC flag to check
* if these entries can be rewriten by arp updates.
*/
lle = lltable_alloc_entry(LLTABLE(ifp), LLE_IFADDR | LLE_STATIC, dst);
if (lle == NULL) {
log(LOG_INFO, "arp_ifinit: cannot create arp "
"entry for interface address\n");
return;
}
IF_AFDATA_WLOCK(ifp);
LLE_WLOCK(lle);
/* Unlink any entry if exists */
lle_tmp = lla_lookup(LLTABLE(ifp), LLE_EXCLUSIVE, dst);
if (lle_tmp != NULL)
lltable_unlink_entry(LLTABLE(ifp), lle_tmp);
lltable_link_entry(LLTABLE(ifp), lle);
IF_AFDATA_WUNLOCK(ifp);
if (lle_tmp != NULL)
EVENTHANDLER_INVOKE(lle_event, lle_tmp, LLENTRY_EXPIRED);
EVENTHANDLER_INVOKE(lle_event, lle, LLENTRY_RESOLVED);
LLE_WUNLOCK(lle);
if (lle_tmp != NULL)
lltable_free_entry(LLTABLE(ifp), lle_tmp);
}
/*
* Handle the garp_rexmit_count. Like sysctl_handle_int(), but limits the range
* of valid values.
*/
static int
sysctl_garp_rexmit(SYSCTL_HANDLER_ARGS)
{
int error;
int rexmit_count = *(int *)arg1;
error = sysctl_handle_int(oidp, &rexmit_count, 0, req);
/* Enforce limits on any new value that may have been set. */
if (!error && req->newptr) {
/* A new value was set. */
if (rexmit_count < 0) {
rexmit_count = 0;
} else if (rexmit_count > MAX_GARP_RETRANSMITS) {
rexmit_count = MAX_GARP_RETRANSMITS;
}
*(int *)arg1 = rexmit_count;
}
return (error);
}
/*
* Retransmit a Gratuitous ARP (GARP) and, if necessary, schedule a callout to
* retransmit it again. A pending callout owns a reference to the ifa.
*/
static void
garp_rexmit(void *arg)
{
struct in_ifaddr *ia = arg;
if (callout_pending(&ia->ia_garp_timer) ||
!callout_active(&ia->ia_garp_timer)) {
IF_ADDR_WUNLOCK(ia->ia_ifa.ifa_ifp);
ifa_free(&ia->ia_ifa);
return;
}
/*
* Drop lock while the ARP request is generated.
*/
IF_ADDR_WUNLOCK(ia->ia_ifa.ifa_ifp);
arprequest(ia->ia_ifa.ifa_ifp, &IA_SIN(ia)->sin_addr,
&IA_SIN(ia)->sin_addr, IF_LLADDR(ia->ia_ifa.ifa_ifp));
/*
* Increment the count of retransmissions. If the count has reached the
* maximum value, stop sending the GARP packets. Otherwise, schedule
* the callout to retransmit another GARP packet.
*/
++ia->ia_garp_count;
if (ia->ia_garp_count >= garp_rexmit_count) {
ifa_free(&ia->ia_ifa);
} else {
int rescheduled;
IF_ADDR_WLOCK(ia->ia_ifa.ifa_ifp);
rescheduled = callout_reset(&ia->ia_garp_timer,
(1 << ia->ia_garp_count) * hz,
garp_rexmit, ia);
IF_ADDR_WUNLOCK(ia->ia_ifa.ifa_ifp);
if (rescheduled) {
ifa_free(&ia->ia_ifa);
}
}
}
/*
* Start the GARP retransmit timer.
*
* A single GARP is always transmitted when an IPv4 address is added
* to an interface and that is usually sufficient. However, in some
* circumstances, such as when a shared address is passed between
* cluster nodes, this single GARP may occasionally be dropped or
* lost. This can lead to neighbors on the network link working with a
* stale ARP cache and sending packets destined for that address to
* the node that previously owned the address, which may not respond.
*
* To avoid this situation, GARP retransmits can be enabled by setting
* the net.link.ether.inet.garp_rexmit_count sysctl to a value greater
* than zero. The setting represents the maximum number of
* retransmissions. The interval between retransmissions is calculated
* using an exponential backoff algorithm, doubling each time, so the
* retransmission intervals are: {1, 2, 4, 8, 16, ...} (seconds).
*/
static void
garp_timer_start(struct ifaddr *ifa)
{
struct in_ifaddr *ia = (struct in_ifaddr *) ifa;
IF_ADDR_WLOCK(ia->ia_ifa.ifa_ifp);
ia->ia_garp_count = 0;
if (callout_reset(&ia->ia_garp_timer, (1 << ia->ia_garp_count) * hz,
garp_rexmit, ia) == 0) {
ifa_ref(ifa);
}
IF_ADDR_WUNLOCK(ia->ia_ifa.ifa_ifp);
}
void
arp_ifinit(struct ifnet *ifp, struct ifaddr *ifa)
{
const struct sockaddr_in *dst_in;
const struct sockaddr *dst;
if (ifa->ifa_carp != NULL)
return;
dst = ifa->ifa_addr;
dst_in = (const struct sockaddr_in *)dst;
if (ntohl(dst_in->sin_addr.s_addr) == INADDR_ANY)
return;
arp_announce_ifaddr(ifp, dst_in->sin_addr, IF_LLADDR(ifp));
if (garp_rexmit_count > 0) {
garp_timer_start(ifa);
}
arp_add_ifa_lle(ifp, dst);
}
void
arp_announce_ifaddr(struct ifnet *ifp, struct in_addr addr, u_char *enaddr)
{
if (ntohl(addr.s_addr) != INADDR_ANY)
arprequest(ifp, &addr, &addr, enaddr);
}
/*
* Sends gratuitous ARPs for each ifaddr to notify other
* nodes about the address change.
*/
static __noinline void
arp_handle_ifllchange(struct ifnet *ifp)
{
struct ifaddr *ifa;
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
if (ifa->ifa_addr->sa_family == AF_INET)
arp_ifinit(ifp, ifa);
}
}
/*
* A handler for interface link layer address change event.
*/
static void
arp_iflladdr(void *arg __unused, struct ifnet *ifp)
{
lltable_update_ifaddr(LLTABLE(ifp));
if ((ifp->if_flags & IFF_UP) != 0)
arp_handle_ifllchange(ifp);
}
static void
vnet_arp_init(void)
{
if (IS_DEFAULT_VNET(curvnet)) {
netisr_register(&arp_nh);
iflladdr_tag = EVENTHANDLER_REGISTER(iflladdr_event,
arp_iflladdr, NULL, EVENTHANDLER_PRI_ANY);
}
#ifdef VIMAGE
else
netisr_register_vnet(&arp_nh);
#endif
}
VNET_SYSINIT(vnet_arp_init, SI_SUB_PROTO_DOMAIN, SI_ORDER_SECOND,
vnet_arp_init, 0);
#ifdef VIMAGE
/*
* We have to unregister ARP along with IP otherwise we risk doing INADDR_HASH
* lookups after destroying the hash. Ideally this would go on SI_ORDER_3.5.
*/
static void
vnet_arp_destroy(__unused void *arg)
{
netisr_unregister_vnet(&arp_nh);
}
VNET_SYSUNINIT(vnet_arp_uninit, SI_SUB_PROTO_DOMAIN, SI_ORDER_THIRD,
vnet_arp_destroy, NULL);
#endif
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