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368 lines
8.2 KiB
C
368 lines
8.2 KiB
C
#include <sys/types.h>
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#include <sys/socket.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include "socket.h"
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#include <errno.h>
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#include "byte.h"
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#include "uint16.h"
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#include "dns.h"
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#include "ip6.h"
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static int serverwantstcp(const char *buf,unsigned int len)
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{
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char out[12];
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if (!dns_packet_copy(buf,len,0,out,12)) return 1;
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if (out[2] & 2) return 1;
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return 0;
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}
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static int serverfailed(const char *buf,unsigned int len)
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{
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char out[12];
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unsigned int rcode;
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if (!dns_packet_copy(buf,len,0,out,12)) return 1;
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rcode = out[3];
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rcode &= 15;
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if (rcode && (rcode != 3)) { errno = EAGAIN; return 1; }
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return 0;
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}
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static int irrelevant(const struct dns_transmit *d,const char *buf,unsigned int len)
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{
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char out[12];
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char *dn;
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unsigned int pos;
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pos = dns_packet_copy(buf,len,0,out,12); if (!pos) return 1;
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if (byte_diff(out,2,d->query + 2)) return 1;
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if (out[4] != 0) return 1;
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if (out[5] != 1) return 1;
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dn = 0;
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pos = dns_packet_getname(buf,len,pos,&dn); if (!pos) return 1;
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if (!dns_domain_equal(dn,d->query + 14)) { free(dn); return 1; }
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free(dn);
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pos = dns_packet_copy(buf,len,pos,out,4); if (!pos) return 1;
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if (byte_diff(out,2,d->qtype)) return 1;
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if (byte_diff(out + 2,2,DNS_C_IN)) return 1;
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return 0;
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}
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static void packetfree(struct dns_transmit *d)
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{
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if (!d->packet) return;
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free(d->packet);
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d->packet = 0;
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}
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static void queryfree(struct dns_transmit *d)
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{
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if (!d->query) return;
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free(d->query);
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d->query = 0;
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}
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static void socketfree(struct dns_transmit *d)
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{
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if (!d->s1) return;
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close(d->s1 - 1);
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d->s1 = 0;
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}
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void dns_transmit_free(struct dns_transmit *d)
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{
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queryfree(d);
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socketfree(d);
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packetfree(d);
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}
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static int randombind(struct dns_transmit *d)
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{
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int j;
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for (j = 0;j < 10;++j)
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if (socket_bind6(d->s1 - 1,d->localip,1025 + dns_random(64510),d->scope_id) == 0)
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return 0;
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if (socket_bind6(d->s1 - 1,d->localip,0,d->scope_id) == 0)
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return 0;
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return -1;
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}
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static const int timeouts[4] = { 1, 3, 11, 45 };
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static int thisudp(struct dns_transmit *d)
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{
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const char *ip;
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socketfree(d);
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while (d->udploop < 4) {
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for (;d->curserver < 16;++d->curserver) {
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ip = d->servers + 16 * d->curserver;
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if (byte_diff(ip,16,V6any)) {
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d->query[2] = dns_random(256);
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d->query[3] = dns_random(256);
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d->s1 = 1 + socket_udp6();
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if (!d->s1) { dns_transmit_free(d); return -1; }
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if (randombind(d) == -1) { dns_transmit_free(d); return -1; }
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if (socket_connect6(d->s1 - 1,ip,53,d->scope_id) == 0)
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if (send(d->s1 - 1,d->query + 2,d->querylen - 2,0) == d->querylen - 2) {
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struct taia now;
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taia_now(&now);
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taia_uint(&d->deadline,timeouts[d->udploop]);
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taia_add(&d->deadline,&d->deadline,&now);
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d->tcpstate = 0;
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return 0;
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}
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socketfree(d);
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}
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}
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++d->udploop;
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d->curserver = 0;
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}
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dns_transmit_free(d); return -1;
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}
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static int firstudp(struct dns_transmit *d)
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{
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d->curserver = 0;
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return thisudp(d);
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}
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static int nextudp(struct dns_transmit *d)
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{
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++d->curserver;
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return thisudp(d);
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}
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static int thistcp(struct dns_transmit *d)
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{
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struct taia now;
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const char *ip;
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socketfree(d);
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packetfree(d);
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for (;d->curserver < 16;++d->curserver) {
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ip = d->servers + 16 * d->curserver;
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if (byte_diff(ip,16,V6any)) {
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d->query[2] = dns_random(256);
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d->query[3] = dns_random(256);
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d->s1 = 1 + socket_tcp6();
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if (!d->s1) { dns_transmit_free(d); return -1; }
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if (randombind(d) == -1) { dns_transmit_free(d); return -1; }
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taia_now(&now);
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taia_uint(&d->deadline,10);
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taia_add(&d->deadline,&d->deadline,&now);
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if (socket_connect6(d->s1 - 1,ip,53,d->scope_id) == 0) {
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d->tcpstate = 2;
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return 0;
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}
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if ((errno == EINPROGRESS) || (errno == EWOULDBLOCK)) {
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d->tcpstate = 1;
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return 0;
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}
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socketfree(d);
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}
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}
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dns_transmit_free(d); return -1;
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}
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static int firsttcp(struct dns_transmit *d)
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{
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d->curserver = 0;
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return thistcp(d);
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}
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static int nexttcp(struct dns_transmit *d)
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{
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++d->curserver;
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return thistcp(d);
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}
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int dns_transmit_start(struct dns_transmit *d,const char servers[256],int flagrecursive,const char *q,const char qtype[2],const char localip[16])
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{
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unsigned int len;
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dns_transmit_free(d);
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errno = EIO;
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len = dns_domain_length(q);
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d->querylen = len + 18;
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d->query = malloc(d->querylen);
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if (!d->query) return -1;
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uint16_pack_big(d->query,len + 16);
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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");
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byte_copy(d->query + 14,len,q);
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byte_copy(d->query + 14 + len,2,qtype);
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byte_copy(d->query + 16 + len,2,DNS_C_IN);
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byte_copy(d->qtype,2,qtype);
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d->servers = servers;
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byte_copy(d->localip,16,localip);
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d->udploop = flagrecursive ? 1 : 0;
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if (len + 16 > 512) return firsttcp(d);
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return firstudp(d);
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}
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void dns_transmit_io(struct dns_transmit *d,iopause_fd *x,struct taia *deadline)
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{
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x->fd = d->s1 - 1;
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switch(d->tcpstate) {
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case 0: case 3: case 4: case 5:
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x->events = IOPAUSE_READ;
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break;
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case 1: case 2:
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x->events = IOPAUSE_WRITE;
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break;
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}
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if (taia_less(&d->deadline,deadline))
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*deadline = d->deadline;
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}
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int dns_transmit_get(struct dns_transmit *d,const iopause_fd *x,const struct taia *when)
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{
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char udpbuf[513];
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unsigned char ch;
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int r;
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int fd;
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errno = EIO;
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fd = d->s1 - 1;
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if (!x->revents) {
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if (taia_less(when,&d->deadline)) return 0;
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errno = ETIMEDOUT;
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if (d->tcpstate == 0) return nextudp(d);
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return nexttcp(d);
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}
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if (d->tcpstate == 0) {
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/*
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have attempted to send UDP query to each server udploop times
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have sent query to curserver on UDP socket s
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*/
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r = recv(fd,udpbuf,sizeof udpbuf,0);
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if (r <= 0) {
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if (errno == ECONNREFUSED) if (d->udploop == 2) return 0;
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return nextudp(d);
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}
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if (r + 1 > sizeof udpbuf) return 0;
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if (irrelevant(d,udpbuf,r)) return 0;
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if (serverwantstcp(udpbuf,r)) return firsttcp(d);
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if (serverfailed(udpbuf,r)) {
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if (d->udploop == 2) return 0;
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return nextudp(d);
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}
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socketfree(d);
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d->packetlen = r;
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d->packet = malloc(d->packetlen);
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if (!d->packet) { dns_transmit_free(d); return -1; }
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byte_copy(d->packet,d->packetlen,udpbuf);
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queryfree(d);
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return 1;
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}
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if (d->tcpstate == 1) {
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/*
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have sent connection attempt to curserver on TCP socket s
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pos not defined
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*/
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if (!socket_connected(fd)) return nexttcp(d);
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d->pos = 0;
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d->tcpstate = 2;
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return 0;
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}
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if (d->tcpstate == 2) {
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/*
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have connection to curserver on TCP socket s
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have sent pos bytes of query
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*/
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r = write(fd,d->query + d->pos,d->querylen - d->pos);
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if (r <= 0) return nexttcp(d);
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d->pos += r;
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if (d->pos == d->querylen) {
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struct taia now;
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taia_now(&now);
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taia_uint(&d->deadline,10);
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taia_add(&d->deadline,&d->deadline,&now);
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d->tcpstate = 3;
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}
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return 0;
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}
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if (d->tcpstate == 3) {
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/*
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have sent entire query to curserver on TCP socket s
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pos not defined
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*/
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r = read(fd,&ch,1);
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if (r <= 0) return nexttcp(d);
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d->packetlen = ch;
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d->tcpstate = 4;
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return 0;
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}
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if (d->tcpstate == 4) {
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/*
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have sent entire query to curserver on TCP socket s
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pos not defined
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have received one byte of packet length into packetlen
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*/
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r = read(fd,&ch,1);
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if (r <= 0) return nexttcp(d);
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d->packetlen <<= 8;
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d->packetlen += ch;
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d->tcpstate = 5;
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d->pos = 0;
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d->packet = malloc(d->packetlen);
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if (!d->packet) { dns_transmit_free(d); return -1; }
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return 0;
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}
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if (d->tcpstate == 5) {
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/*
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have sent entire query to curserver on TCP socket s
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have received entire packet length into packetlen
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packet is allocated
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have received pos bytes of packet
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*/
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r = read(fd,d->packet + d->pos,d->packetlen - d->pos);
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if (r <= 0) return nexttcp(d);
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d->pos += r;
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if (d->pos < d->packetlen) return 0;
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socketfree(d);
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if (irrelevant(d,d->packet,d->packetlen)) return nexttcp(d);
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if (serverwantstcp(d->packet,d->packetlen)) return nexttcp(d);
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if (serverfailed(d->packet,d->packetlen)) return nexttcp(d);
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queryfree(d);
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return 1;
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}
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return 0;
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}
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