ref: 6cd07cf340af12356ca4558cb8fad5ed3ebc41d1
dir: /sys/src/9/ip/arp.c/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
#include "ip.h"
#include "ipv6.h"
/*
* address resolution tables
*/
enum
{
NHASH = (1<<6),
NCACHE = 256,
AOK = 1,
AWAIT = 2,
MAXAGE_TIMER = 15*60*1000,
};
char *arpstate[] =
{
"UNUSED",
"OK",
"WAIT",
};
/*
* one per Fs
*/
struct Arp
{
RWlock;
Fs *f;
Arpent *hash[NHASH];
Arpent cache[NCACHE];
Arpent *rxmt[2];
Proc *rxmitp; /* neib sol re-transmit proc */
Rendez rxmtq;
Block *dropf, *dropl;
};
char *Ebadarp = "bad arp";
/* quick hash for ip addresses */
#define hashipa(a) (((a)[IPaddrlen-2] + (a)[IPaddrlen-1])%NHASH)
static void rxmitproc(void*);
void
arpinit(Fs *f)
{
f->arp = smalloc(sizeof(Arp));
f->arp->f = f;
f->arp->rxmt[0] = nil;
f->arp->rxmt[1] = nil;
f->arp->dropf = f->arp->dropl = nil;
kproc("rxmitproc", rxmitproc, f->arp);
}
static void
freeblistchain(Block *bp)
{
Block *next;
while(bp != nil){
next = bp->list;
freeblist(bp);
bp = next;
}
}
/* take out of re-transmit chain */
static Arpent**
rxmtunchain(Arp *arp, Arpent *a)
{
Arpent **l;
for(l = &arp->rxmt[isv4(a->ip) != 0]; *l != nil; l = &((*l)->nextrxt)){
if(*l == a){
*l = a->nextrxt;
break;
}
}
a->nextrxt = nil;
return l;
}
static void
cleanarpent(Arp *arp, Arpent *a)
{
Arpent **l;
Block *bp;
/* take out of current chain */
for(l = &arp->hash[hashipa(a->ip)]; *l != nil; l = &((*l)->hash)){
if(*l == a){
*l = a->hash;
break;
}
}
a->hash = nil;
/* remove from retransmit / timout chain */
rxmtunchain(arp, a);
/* queue packets for icmp unreachable for rxmitproc later on, w/o arp lock */
if((bp = a->hold) != nil){
if(arp->dropf == nil)
arp->dropf = bp;
else
arp->dropl->list = bp;
arp->dropl = a->last;
if(bp == arp->dropf)
wakeup(&arp->rxmtq);
}
a->hold = nil;
a->last = nil;
a->ifc = nil;
a->ifcid = 0;
a->state = 0;
a->rxtsrem = 0;
a->utime = 0;
a->ctime = 0;
}
/*
* create a new arp entry for an ip address on ifc.
*/
static Arpent*
newarpent(Arp *arp, uchar *ip, Ipifc *ifc)
{
Arpent *a, *e, *f, **l;
ulong t;
/* find oldest entry */
e = &arp->cache[NCACHE];
a = arp->cache;
t = a->utime;
for(f = a+1; t > 0 && f < e; f++){
if(f->utime < t){
t = f->utime;
a = f;
}
}
cleanarpent(arp, a);
ipmove(a->ip, ip);
a->ifc = ifc;
a->ifcid = ifc->ifcid;
/* insert into new chain */
l = &arp->hash[hashipa(ip)];
a->hash = *l;
*l = a;
return a;
}
static Arpent*
arplookup(Arp *arp, Ipifc *ifc, uchar *ip)
{
Arpent *a;
for(a = arp->hash[hashipa(ip)]; a != nil; a = a->hash){
if(a->ifc == ifc && a->ifcid == ifc->ifcid && ipcmp(ip, a->ip) == 0)
return a;
}
return nil;
}
static int
arphit(Arpent *a, uchar *mac, int maclen, Routehint *rh)
{
if(a->state == AOK){
memmove(mac, a->mac, maclen);
a->utime = NOW;
if(a->utime - a->ctime < MAXAGE_TIMER){
if(rh != nil)
rh->a = a;
return 1;
}
}
return 0;
}
/*
* fill in the media address if we have it. Otherwise return an
* Arpent that represents the state of the address resolution FSM
* for ip. Add the packet to be sent onto the list of packets
* waiting for ip->mac to be resolved.
*/
Arpent*
arpget(Arp *arp, Block *bp, int version, Ipifc *ifc, uchar *ip, uchar *mac, Routehint *rh)
{
uchar v6ip[IPaddrlen];
Arpent *a;
if(version == V4){
v4tov6(v6ip, ip);
ip = v6ip;
}
if(rh != nil
&& (a = rh->a) != nil
&& a->ifc == ifc
&& a->ifcid == ifc->ifcid
&& ipcmp(ip, a->ip) == 0
&& arphit(a, mac, ifc->m->maclen, nil))
return nil;
rlock(arp);
if((a = arplookup(arp, ifc, ip)) != nil
&& arphit(a, mac, ifc->m->maclen, rh)){
runlock(arp);
return nil;
}
if(rh != nil)
rh->a = nil;
runlock(arp);
wlock(arp);
if((a = arplookup(arp, ifc, ip)) == nil)
a = newarpent(arp, ip, ifc);
else if(arphit(a, mac, ifc->m->maclen, rh)){
wunlock(arp);
return nil;
}
a->state = AWAIT;
a->utime = NOW;
if(bp != nil){
/* needs to be a single block */
assert(bp->list == nil);
if(a->hold == nil)
a->hold = bp;
else
a->last->list = bp;
a->last = bp;
}
return a; /* return with arp locked */
}
/*
* continue address resolution for the entry,
* schedule it on the retransmit / timeout chains
* and unlock the arp cache.
*/
void
arpcontinue(Arp *arp, Arpent *a)
{
Arpent **l;
Block *bp;
/* remove all but the last message */
while((bp = a->hold) != nil){
if(bp == a->last)
break;
a->hold = bp->list;
freeblist(bp);
}
/* try to keep it around for a second more */
a->ctime = a->utime = NOW;
/* put on end of re-transmit / timeout chain */
for(l = rxmtunchain(arp, a); *l != nil; l = &(*l)->nextrxt)
;
*l = a;
if(l == &arp->rxmt[0] || l == &arp->rxmt[1])
wakeup(&arp->rxmtq);
wunlock(arp);
}
/*
* called with arp locked
*/
void
arprelease(Arp *arp, Arpent*)
{
wunlock(arp);
}
/*
* Copy out the mac address from the Arpent. Return the
* first block waiting to get sent to this mac address.
*
* called with arp locked
*/
Block*
arpresolve(Arp *arp, Arpent *a, uchar *mac, Routehint *rh)
{
Block *bp;
memmove(a->mac, mac, a->ifc->m->maclen);
if(a->state == AWAIT) {
rxmtunchain(arp, a);
a->rxtsrem = 0;
}
bp = a->hold;
a->hold = a->last = nil;
a->ctime = a->utime = NOW;
a->state = AOK;
if(rh != nil)
rh->a = a;
wunlock(arp);
if(bp != nil){
freeblistchain(bp->list);
bp->list = nil;
}
return bp;
}
int
arpenter(Fs *fs, int version, uchar *ip, uchar *mac, int maclen, uchar *ia, Ipifc *ifc, int refresh)
{
Routehint rh;
uchar v6ip[IPaddrlen];
Block *bp, *next;
Arpent *a;
Route *r;
Arp *arp;
if(ifc->m == nil || maclen < ifc->m->maclen || ifc->m->maclen == 0)
return -1;
rh.r = nil;
rh.a = nil;
switch(version){
case V4:
r = v4lookup(fs, ip, ia, &rh);
v4tov6(v6ip, ip);
ip = v6ip;
break;
case V6:
r = v6lookup(fs, ip, ia, &rh);
break;
default:
panic("arpenter: version %d", version);
}
if(r == nil || r->ifc != ifc || (r->type & (Rbcast|Rmulti)) != 0)
return -1;
arp = fs->arp;
wlock(arp);
if((a = arplookup(arp, ifc, ip)) == nil){
if(refresh){
wunlock(arp);
return 0;
}
a = newarpent(arp, ip, ifc);
}
bp = a->hold;
a->hold = a->last = nil;
arpresolve(arp, a, mac, &rh); /* unlocks arp */
if(version == V4)
ip += IPv4off;
for(; bp != nil; bp = next){
next = bp->list;
bp->list = nil;
if(waserror()){
freeblistchain(next);
break;
}
ipifcoput(ifc, bp, version, ip, &rh);
poperror();
}
return 1;
}
/*
* arpforme() checks if we should respond to arp/ndp on a specific interface.
*
* returns Runi if targ is a non-tentative local address on ifc.
* returns Rproxy if we have a proxy route for targ to another interface.
*/
int
arpforme(Fs *fs, int version, uchar *targ, uchar *src, Ipifc *ifc)
{
uchar ipv6[IPaddrlen];
Iplifc *lifc;
Route *r;
if(version == V4) {
v4tov6(ipv6, targ);
targ = ipv6;
}
lifc = iplocalonifc(ifc, targ);
if(lifc != nil){
if(lifc->tentative)
return 0;
return Runi;
}
if(version == V4){
targ += IPv4off;
r = v4lookup(fs, targ, src, nil);
} else {
r = v6lookup(fs, targ, src, nil);
}
if(r == nil || r->ifc == ifc && r->ifcid == ifc->ifcid)
return 0;
return r->type & Rproxy;
}
int
arpwrite(Fs *fs, char *s, int len)
{
int n;
Arp *arp;
Arpent *a, *x;
Medium *m;
Ipifc *ifc;
char *f[5], buf[256];
uchar ip[IPaddrlen], ia[IPaddrlen], mac[MAClen];
arp = fs->arp;
if(len == 0)
error(Ebadarp);
if(len >= sizeof(buf))
len = sizeof(buf)-1;
strncpy(buf, s, len);
buf[len] = 0;
if(len > 0 && buf[len-1] == '\n')
buf[len-1] = 0;
n = getfields(buf, f, nelem(f), 1, " ");
if(strcmp(f[0], "flush") == 0){
wlock(arp);
for(a = arp->cache; a < &arp->cache[NCACHE]; a++){
a->hash = nil;
a->nextrxt = nil;
a->ifc = nil;
a->ifcid = 0;
a->state = 0;
a->rxtsrem = 0;
a->ctime = 0;
a->utime = 0;
freeblistchain(a->hold);
a->hold = a->last = nil;
}
memset(arp->hash, 0, sizeof(arp->hash));
freeblistchain(arp->dropf);
arp->dropf = arp->dropl = nil;
arp->rxmt[0] = arp->rxmt[1] = nil;
wunlock(arp);
} else if(strcmp(f[0], "add") == 0){
switch(n){
default:
error(Ebadarg);
case 3:
if(parseip(ip, f[1]) == -1)
error(Ebadip);
if((n = parsemac(mac, f[2], sizeof(mac))) <= 0)
error(Ebadarp);
findlocalip(fs, ia, ip);
break;
case 4:
m = ipfindmedium(f[1]);
if(m == nil || m->maclen == 0)
error(Ebadarp);
if(parseip(ip, f[2]) == -1)
error(Ebadip);
if((n = parsemac(mac, f[3], sizeof(mac))) != m->maclen)
error(Ebadarp);
findlocalip(fs, ia, ip);
break;
case 5:
m = ipfindmedium(f[1]);
if(m == nil || m->maclen == 0)
error(Ebadarp);
if(parseip(ip, f[2]) == -1)
error(Ebadip);
if((n = parsemac(mac, f[3], sizeof(mac))) != m->maclen)
error(Ebadarp);
if(parseip(ia, f[4]) == -1)
error(Ebadip);
break;
}
if((ifc = findipifc(fs, ia, ia, Runi)) == nil)
error("no interface");
if(!ipv6local(ifc, ia, 0, ip) || arpenter(fs, V6, ip, mac, n, ia, ifc, 0) < 0){
runlock(ifc);
error("destination unreachable");
}
runlock(ifc);
} else if(strcmp(f[0], "del") == 0){
if(n != 2)
error(Ebadarg);
if(parseip(ip, f[1]) == -1)
error(Ebadip);
wlock(arp);
for(a = arp->hash[hashipa(ip)]; a != nil; a = x){
x = a->hash;
if(ipcmp(ip, a->ip) == 0)
cleanarpent(arp, a);
}
wunlock(arp);
} else if(strcmp(f[0], "garp") == 0){
Iplifc *lifc;
if(n != 2)
error(Ebadarg);
if(parseip(ip, f[1]) == -1)
error(Ebadip);
if((ifc = findipifc(fs, ip, ip, Runi)) == nil)
error("no interface");
if(waserror()){
runlock(ifc);
nexterror();
}
if(ifc->m != nil && ifc->m->areg != nil && (lifc = iplocalonifc(ifc, ip)) != nil)
(*ifc->m->areg)(fs, ifc, lifc, ip);
runlock(ifc);
poperror();
} else
error(Ebadarp);
return len;
}
static void
convmac(char *p, uchar *mac, int n)
{
while(n-- > 0)
p += sprint(p, "%2.2ux", *mac++);
}
int
arpread(Arp *arp, char *s, ulong offset, int len)
{
char mac[2*MAClen+1], *state, *mname, *p;
uchar ip[IPaddrlen], ia[IPaddrlen];
Ipifc *ifc;
Arpent *a;
long n, o;
p = s;
o = -offset;
for(a = arp->cache; len > 0 && a < &arp->cache[NCACHE]; a++){
if(a->state == 0 || (ifc = a->ifc) == nil)
continue;
rlock(ifc);
rlock(arp);
ipmove(ip, a->ip);
if(ifc->m == nil || a->state == 0 || a->ifc != ifc || a->ifcid != ifc->ifcid || !ipv6local(ifc, ia, 0, ip)){
runlock(arp);
runlock(ifc);
continue;
}
mname = ifc->m->name;
state = arpstate[a->state];
convmac(mac, a->mac, ifc->m->maclen);
runlock(arp);
runlock(ifc);
n = snprint(up->genbuf, sizeof up->genbuf,
"%-6.6s %-4.4s %-40.40I %-16.16s %I\n",
mname, state, ip, mac, ia);
o += n;
if(o <= 0)
continue;
if(n > len)
break;
memmove(p, up->genbuf, n);
len -= n;
p += n;
}
return p - s;
}
void
ndpsendsol(Fs *f, Arpent *a)
{
Ipifc *ifc = a->ifc;
uchar targ[IPaddrlen], src[IPaddrlen];
if(a->rxtsrem == 0)
a->rxtsrem = MAX_MULTICAST_SOLICIT;
else
a->rxtsrem--;
/* try to use source address of original packet */
ipmove(targ, a->ip);
if(a->last != nil){
ipmove(src, ((Ip6hdr*)a->last->rp)->src);
arpcontinue(f->arp, a);
if(arpforme(f, V6, src, targ, ifc))
goto send;
} else {
arpcontinue(f->arp, a);
}
if(!ipv6local(ifc, src, 0, targ))
return;
send:
if(!waserror()){
icmpns6(f, src, SRC_UNI, targ, TARG_MULTI, ifc->mac, ifc->m->maclen);
poperror();
}
}
static Block*
rxmt(Arp *arp)
{
Arpent *a;
Block *bp;
Ipifc *ifc;
wlock(arp);
/* retransmit ipv6 solicitations */
while((a = arp->rxmt[0]) != nil && NOW - a->ctime > 3*RETRANS_TIMER/4){
if(a->rxtsrem > 0 && (ifc = a->ifc) != nil && canrlock(ifc)){
if(a->ifcid == ifc->ifcid){
ndpsendsol(arp->f, a); /* unlocks arp */
runlock(ifc);
wlock(arp);
continue;
}
runlock(ifc);
}
cleanarpent(arp, a);
}
/* timeout waiting ipv4 arp entries */
while((a = arp->rxmt[1]) != nil && NOW - a->ctime > 3*RETRANS_TIMER)
cleanarpent(arp, a);
bp = arp->dropf;
arp->dropf = arp->dropl = nil;
wunlock(arp);
return bp;
}
static void
drop(Fs *f, Block *bp)
{
Routehint rh;
Route *r;
Ipifc *ifc;
Block *next;
for(; bp != nil; bp = next){
next = bp->list;
bp->list = nil;
rh.r = nil;
rh.a = nil;
if((bp->rp[0]&0xF0) == IP_VER4)
r = v4lookup(f, ((Ip4hdr*)bp->rp)->src, ((Ip4hdr*)bp->rp)->dst, &rh);
else
r = v6lookup(f, ((Ip6hdr*)bp->rp)->src, ((Ip6hdr*)bp->rp)->dst, &rh);
if(r != nil && (ifc = r->ifc) != nil && canrlock(ifc)){
if(ifc->ifcid == r->ifcid && !waserror()){
if((bp->rp[0]&0xF0) == IP_VER4)
icmpnohost(f, ifc, bp, &rh);
else
icmpnohost6(f, ifc, bp, &rh);
poperror();
}
runlock(ifc);
}
freeblist(bp);
}
}
static int
rxready(void *v)
{
Arp *arp = (Arp *)v;
return arp->rxmt[0] != nil || arp->rxmt[1] != nil || arp->dropf != nil;
}
static void
rxmitproc(void *v)
{
Arp *arp = v;
arp->rxmitp = up;
if(waserror()){
arp->rxmitp = nil;
pexit("hangup", 1);
}
for(;;){
sleep(&arp->rxmtq, rxready, v);
drop(arp->f, rxmt(arp));
tsleep(&arp->rxmtq, return0, nil, RETRANS_TIMER/4);
}
}