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#include <u.h>
#include <libc.h>
#include <ip.h>
#include "dns.h"
/*
* a dictionary of domain names for packing messages
*/
enum
{
Ndict= 64,
};
typedef struct Dict Dict;
struct Dict
{
struct {
ushort offset; /* pointer to packed name in message */
char *name; /* pointer to unpacked name in buf */
} x[Ndict];
int n; /* size of dictionary */
uchar *start; /* start of packed message */
char buf[16*1024]; /* buffer for unpacked names (was 4k) */
char *ep; /* first free char in buf */
};
#define NAME(x) p = pname(p, ep, x, dp)
#define SYMBOL(x) p = psym(p, ep, x)
#define STRING(x) p = pstr(p, ep, x)
#define BYTES(x, n) p = pbytes(p, ep, x, n)
#define USHORT(x) p = pushort(p, ep, x)
#define UCHAR(x) p = puchar(p, ep, x)
#define ULONG(x) p = pulong(p, ep, x)
#define V4ADDR(x) p = pv4addr(p, ep, x)
#define V6ADDR(x) p = pv6addr(p, ep, x)
static uchar*
psym(uchar *p, uchar *ep, char *np)
{
int n;
n = strlen(np);
if(n >= Strlen) /* DNS maximum length string */
n = Strlen - 1;
if(ep - p < n+1) /* see if it fits in the buffer */
return ep+1;
*p++ = n;
memmove(p, np, n);
return p + n;
}
static uchar*
pstr(uchar *p, uchar *ep, char *np)
{
return psym(p, ep, np);
}
static uchar*
pbytes(uchar *p, uchar *ep, uchar *np, int n)
{
if(ep - p < n)
return ep+1;
memmove(p, np, n);
return p + n;
}
static uchar*
puchar(uchar *p, uchar *ep, int val)
{
if(ep - p < 1)
return ep+1;
*p++ = val;
return p;
}
static uchar*
pushort(uchar *p, uchar *ep, int val)
{
if(ep - p < 2)
return ep+1;
*p++ = val>>8;
*p++ = val;
return p;
}
static uchar*
pulong(uchar *p, uchar *ep, int val)
{
if(ep - p < 4)
return ep+1;
*p++ = val>>24;
*p++ = val>>16;
*p++ = val>>8;
*p++ = val;
return p;
}
static uchar*
pv4addr(uchar *p, uchar *ep, char *name)
{
uchar ip[IPaddrlen];
if(ep - p < 4)
return ep+1;
parseip(ip, name);
v6tov4(p, ip);
return p + 4;
}
static uchar*
pv6addr(uchar *p, uchar *ep, char *name)
{
if(ep - p < IPaddrlen)
return ep+1;
parseip(p, name);
return p + IPaddrlen;
}
static uchar*
pname(uchar *p, uchar *ep, char *np, Dict *dp)
{
int i;
char *cp;
char *last; /* last component packed */
if(strlen(np) >= Domlen) /* make sure we don't exceed DNS limits */
return ep+1;
last = 0;
while(*np){
/* look through every component in the dictionary for a match */
for(i = 0; i < dp->n; i++)
if(strcmp(np, dp->x[i].name) == 0){
if(ep - p < 2)
return ep+1;
if ((dp->x[i].offset>>8) & 0xc0)
dnslog("convDNS2M: offset too big for "
"DNS packet format");
*p++ = dp->x[i].offset>>8 | 0xc0;
*p++ = dp->x[i].offset;
return p;
}
/* if there's room, enter this name in dictionary */
if(dp->n < Ndict)
if(last){
/* the whole name is already in dp->buf */
last = strchr(last, '.') + 1;
dp->x[dp->n].name = last;
dp->x[dp->n].offset = p - dp->start;
dp->n++;
} else {
/* add to dp->buf */
i = strlen(np);
if(dp->ep + i + 1 < &dp->buf[sizeof dp->buf]){
strcpy(dp->ep, np);
dp->x[dp->n].name = dp->ep;
last = dp->ep;
dp->x[dp->n].offset = p - dp->start;
dp->ep += i + 1;
dp->n++;
}
}
/* put next component into message */
cp = strchr(np, '.');
if(cp == nil){
i = strlen(np);
cp = np + i; /* point to null terminator */
} else {
i = cp - np;
cp++; /* point past '.' */
}
if(ep-p < i+1)
return ep+1;
if (i > Labellen)
return ep+1;
*p++ = i; /* count of chars in label */
memmove(p, np, i);
np = cp;
p += i;
}
if(p >= ep)
return ep+1;
*p++ = 0; /* add top level domain */
return p;
}
static uchar*
convRR2M(RR *rp, uchar *p, uchar *ep, Dict *dp)
{
uchar *lp, *data;
int len, ttl;
Txt *t;
NAME(rp->owner->name);
USHORT(rp->type);
USHORT(rp->owner->class);
/* egregious overuse of ttl (it's absolute time in the cache) */
if(rp->db)
ttl = rp->ttl;
else
ttl = rp->ttl - now;
if(ttl < 0)
ttl = 0;
ULONG(ttl);
lp = p; /* leave room for the rdata length */
p += 2;
data = p;
if(data >= ep)
return p+1;
switch(rp->type){
case Thinfo:
SYMBOL(rp->cpu->name);
SYMBOL(rp->os->name);
break;
case Tcname:
case Tmb:
case Tmd:
case Tmf:
case Tns:
NAME(rp->host->name);
break;
case Tmg:
case Tmr:
NAME(rp->mb->name);
break;
case Tminfo:
NAME(rp->rmb->name);
NAME(rp->mb->name);
break;
case Tmx:
USHORT(rp->pref);
NAME(rp->host->name);
break;
case Ta:
V4ADDR(rp->ip->name);
break;
case Taaaa:
V6ADDR(rp->ip->name);
break;
case Tptr:
NAME(rp->ptr->name);
break;
case Tsoa:
NAME(rp->host->name);
NAME(rp->rmb->name);
ULONG(rp->soa->serial);
ULONG(rp->soa->refresh);
ULONG(rp->soa->retry);
ULONG(rp->soa->expire);
ULONG(rp->soa->minttl);
break;
case Tsrv:
USHORT(rp->srv->pri);
USHORT(rp->srv->weight);
USHORT(rp->port);
STRING(rp->host->name); /* rfc2782 sez no name compression */
break;
case Ttxt:
for(t = rp->txt; t != nil; t = t->next)
STRING(t->p);
break;
case Tnull:
BYTES(rp->null->data, rp->null->dlen);
break;
case Trp:
NAME(rp->rmb->name);
NAME(rp->rp->name);
break;
case Tkey:
USHORT(rp->key->flags);
UCHAR(rp->key->proto);
UCHAR(rp->key->alg);
BYTES(rp->key->data, rp->key->dlen);
break;
case Tsig:
USHORT(rp->sig->type);
UCHAR(rp->sig->alg);
UCHAR(rp->sig->labels);
ULONG(rp->sig->ttl);
ULONG(rp->sig->exp);
ULONG(rp->sig->incep);
USHORT(rp->sig->tag);
NAME(rp->sig->signer->name);
BYTES(rp->sig->data, rp->sig->dlen);
break;
case Tcert:
USHORT(rp->cert->type);
USHORT(rp->cert->tag);
UCHAR(rp->cert->alg);
BYTES(rp->cert->data, rp->cert->dlen);
break;
}
/* stuff in the rdata section length */
len = p - data;
*lp++ = len >> 8;
*lp = len;
return p;
}
static uchar*
convQ2M(RR *rp, uchar *p, uchar *ep, Dict *dp)
{
NAME(rp->owner->name);
USHORT(rp->type);
USHORT(rp->owner->class);
return p;
}
static uchar*
rrloop(RR *rp, int *countp, uchar *p, uchar *ep, Dict *dp, int quest)
{
uchar *np;
*countp = 0;
for(; rp && p < ep; rp = rp->next){
if(quest)
np = convQ2M(rp, p, ep, dp);
else
np = convRR2M(rp, p, ep, dp);
if(np > ep)
break;
p = np;
(*countp)++;
}
return p;
}
/*
* convert into a message
*/
int
convDNS2M(DNSmsg *m, uchar *buf, int len)
{
ulong trunc = 0;
uchar *p, *ep, *np;
Dict d;
d.n = 0;
d.start = buf;
d.ep = d.buf;
memset(buf, 0, len);
m->qdcount = m->ancount = m->nscount = m->arcount = 0;
/* first pack in the RR's so we can get real counts */
p = buf + 12;
ep = buf + len;
p = rrloop(m->qd, &m->qdcount, p, ep, &d, 1);
p = rrloop(m->an, &m->ancount, p, ep, &d, 0);
p = rrloop(m->ns, &m->nscount, p, ep, &d, 0);
p = rrloop(m->ar, &m->arcount, p, ep, &d, 0);
if(p > ep) {
trunc = Ftrunc;
dnslog("udp packet full; truncating my reply");
p = ep;
}
/* now pack the rest */
np = p;
p = buf;
ep = buf + len;
USHORT(m->id);
USHORT(m->flags | trunc);
USHORT(m->qdcount);
USHORT(m->ancount);
USHORT(m->nscount);
USHORT(m->arcount);
USED(p);
return np - buf;
}