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df36440 Dec 3, 2008
D. J. Bernstein import djbdns 1.03
367 lines (307 sloc) 8.14 KB
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include "socket.h"
#include "alloc.h"
#include "error.h"
#include "byte.h"
#include "uint16.h"
#include "dns.h"
static int serverwantstcp(const char *buf,unsigned int len)
{
char out[12];
if (!dns_packet_copy(buf,len,0,out,12)) return 1;
if (out[2] & 2) return 1;
return 0;
}
static int serverfailed(const char *buf,unsigned int len)
{
char out[12];
unsigned int rcode;
if (!dns_packet_copy(buf,len,0,out,12)) return 1;
rcode = out[3];
rcode &= 15;
if (rcode && (rcode != 3)) { errno = error_again; return 1; }
return 0;
}
static int irrelevant(const struct dns_transmit *d,const char *buf,unsigned int len)
{
char out[12];
char *dn;
unsigned int pos;
pos = dns_packet_copy(buf,len,0,out,12); if (!pos) return 1;
if (byte_diff(out,2,d->query + 2)) return 1;
if (out[4] != 0) return 1;
if (out[5] != 1) return 1;
dn = 0;
pos = dns_packet_getname(buf,len,pos,&dn); if (!pos) return 1;
if (!dns_domain_equal(dn,d->query + 14)) { alloc_free(dn); return 1; }
alloc_free(dn);
pos = dns_packet_copy(buf,len,pos,out,4); if (!pos) return 1;
if (byte_diff(out,2,d->qtype)) return 1;
if (byte_diff(out + 2,2,DNS_C_IN)) return 1;
return 0;
}
static void packetfree(struct dns_transmit *d)
{
if (!d->packet) return;
alloc_free(d->packet);
d->packet = 0;
}
static void queryfree(struct dns_transmit *d)
{
if (!d->query) return;
alloc_free(d->query);
d->query = 0;
}
static void socketfree(struct dns_transmit *d)
{
if (!d->s1) return;
close(d->s1 - 1);
d->s1 = 0;
}
void dns_transmit_free(struct dns_transmit *d)
{
queryfree(d);
socketfree(d);
packetfree(d);
}
static int randombind(struct dns_transmit *d)
{
int j;
for (j = 0;j < 10;++j)
if (socket_bind4(d->s1 - 1,d->localip,1025 + dns_random(64510)) == 0)
return 0;
if (socket_bind4(d->s1 - 1,d->localip,0) == 0)
return 0;
return -1;
}
static const int timeouts[4] = { 1, 3, 11, 45 };
static int thisudp(struct dns_transmit *d)
{
const char *ip;
socketfree(d);
while (d->udploop < 4) {
for (;d->curserver < 16;++d->curserver) {
ip = d->servers + 4 * d->curserver;
if (byte_diff(ip,4,"\0\0\0\0")) {
d->query[2] = dns_random(256);
d->query[3] = dns_random(256);
d->s1 = 1 + socket_udp();
if (!d->s1) { dns_transmit_free(d); return -1; }
if (randombind(d) == -1) { dns_transmit_free(d); return -1; }
if (socket_connect4(d->s1 - 1,ip,53) == 0)
if (send(d->s1 - 1,d->query + 2,d->querylen - 2,0) == d->querylen - 2) {
struct taia now;
taia_now(&now);
taia_uint(&d->deadline,timeouts[d->udploop]);
taia_add(&d->deadline,&d->deadline,&now);
d->tcpstate = 0;
return 0;
}
socketfree(d);
}
}
++d->udploop;
d->curserver = 0;
}
dns_transmit_free(d); return -1;
}
static int firstudp(struct dns_transmit *d)
{
d->curserver = 0;
return thisudp(d);
}
static int nextudp(struct dns_transmit *d)
{
++d->curserver;
return thisudp(d);
}
static int thistcp(struct dns_transmit *d)
{
struct taia now;
const char *ip;
socketfree(d);
packetfree(d);
for (;d->curserver < 16;++d->curserver) {
ip = d->servers + 4 * d->curserver;
if (byte_diff(ip,4,"\0\0\0\0")) {
d->query[2] = dns_random(256);
d->query[3] = dns_random(256);
d->s1 = 1 + socket_tcp();
if (!d->s1) { dns_transmit_free(d); return -1; }
if (randombind(d) == -1) { dns_transmit_free(d); return -1; }
taia_now(&now);
taia_uint(&d->deadline,10);
taia_add(&d->deadline,&d->deadline,&now);
if (socket_connect4(d->s1 - 1,ip,53) == 0) {
d->tcpstate = 2;
return 0;
}
if ((errno == error_inprogress) || (errno == error_wouldblock)) {
d->tcpstate = 1;
return 0;
}
socketfree(d);
}
}
dns_transmit_free(d); return -1;
}
static int firsttcp(struct dns_transmit *d)
{
d->curserver = 0;
return thistcp(d);
}
static int nexttcp(struct dns_transmit *d)
{
++d->curserver;
return thistcp(d);
}
int dns_transmit_start(struct dns_transmit *d,const char servers[64],int flagrecursive,const char *q,const char qtype[2],const char localip[4])
{
unsigned int len;
dns_transmit_free(d);
errno = error_io;
len = dns_domain_length(q);
d->querylen = len + 18;
d->query = alloc(d->querylen);
if (!d->query) return -1;
uint16_pack_big(d->query,len + 16);
byte_copy(d->query + 2,12,flagrecursive ? "\0\0\1\0\0\1\0\0\0\0\0\0" : "\0\0\0\0\0\1\0\0\0\0\0\0gcc-bug-workaround");
byte_copy(d->query + 14,len,q);
byte_copy(d->query + 14 + len,2,qtype);
byte_copy(d->query + 16 + len,2,DNS_C_IN);
byte_copy(d->qtype,2,qtype);
d->servers = servers;
byte_copy(d->localip,4,localip);
d->udploop = flagrecursive ? 1 : 0;
if (len + 16 > 512) return firsttcp(d);
return firstudp(d);
}
void dns_transmit_io(struct dns_transmit *d,iopause_fd *x,struct taia *deadline)
{
x->fd = d->s1 - 1;
switch(d->tcpstate) {
case 0: case 3: case 4: case 5:
x->events = IOPAUSE_READ;
break;
case 1: case 2:
x->events = IOPAUSE_WRITE;
break;
}
if (taia_less(&d->deadline,deadline))
*deadline = d->deadline;
}
int dns_transmit_get(struct dns_transmit *d,const iopause_fd *x,const struct taia *when)
{
char udpbuf[513];
unsigned char ch;
int r;
int fd;
errno = error_io;
fd = d->s1 - 1;
if (!x->revents) {
if (taia_less(when,&d->deadline)) return 0;
errno = error_timeout;
if (d->tcpstate == 0) return nextudp(d);
return nexttcp(d);
}
if (d->tcpstate == 0) {
/*
have attempted to send UDP query to each server udploop times
have sent query to curserver on UDP socket s
*/
r = recv(fd,udpbuf,sizeof udpbuf,0);
if (r <= 0) {
if (errno == error_connrefused) if (d->udploop == 2) return 0;
return nextudp(d);
}
if (r + 1 > sizeof udpbuf) return 0;
if (irrelevant(d,udpbuf,r)) return 0;
if (serverwantstcp(udpbuf,r)) return firsttcp(d);
if (serverfailed(udpbuf,r)) {
if (d->udploop == 2) return 0;
return nextudp(d);
}
socketfree(d);
d->packetlen = r;
d->packet = alloc(d->packetlen);
if (!d->packet) { dns_transmit_free(d); return -1; }
byte_copy(d->packet,d->packetlen,udpbuf);
queryfree(d);
return 1;
}
if (d->tcpstate == 1) {
/*
have sent connection attempt to curserver on TCP socket s
pos not defined
*/
if (!socket_connected(fd)) return nexttcp(d);
d->pos = 0;
d->tcpstate = 2;
return 0;
}
if (d->tcpstate == 2) {
/*
have connection to curserver on TCP socket s
have sent pos bytes of query
*/
r = write(fd,d->query + d->pos,d->querylen - d->pos);
if (r <= 0) return nexttcp(d);
d->pos += r;
if (d->pos == d->querylen) {
struct taia now;
taia_now(&now);
taia_uint(&d->deadline,10);
taia_add(&d->deadline,&d->deadline,&now);
d->tcpstate = 3;
}
return 0;
}
if (d->tcpstate == 3) {
/*
have sent entire query to curserver on TCP socket s
pos not defined
*/
r = read(fd,&ch,1);
if (r <= 0) return nexttcp(d);
d->packetlen = ch;
d->tcpstate = 4;
return 0;
}
if (d->tcpstate == 4) {
/*
have sent entire query to curserver on TCP socket s
pos not defined
have received one byte of packet length into packetlen
*/
r = read(fd,&ch,1);
if (r <= 0) return nexttcp(d);
d->packetlen <<= 8;
d->packetlen += ch;
d->tcpstate = 5;
d->pos = 0;
d->packet = alloc(d->packetlen);
if (!d->packet) { dns_transmit_free(d); return -1; }
return 0;
}
if (d->tcpstate == 5) {
/*
have sent entire query to curserver on TCP socket s
have received entire packet length into packetlen
packet is allocated
have received pos bytes of packet
*/
r = read(fd,d->packet + d->pos,d->packetlen - d->pos);
if (r <= 0) return nexttcp(d);
d->pos += r;
if (d->pos < d->packetlen) return 0;
socketfree(d);
if (irrelevant(d,d->packet,d->packetlen)) return nexttcp(d);
if (serverwantstcp(d->packet,d->packetlen)) return nexttcp(d);
if (serverfailed(d->packet,d->packetlen)) return nexttcp(d);
queryfree(d);
return 1;
}
return 0;
}
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