diff options
Diffstat (limited to 'dnsstub/dns_transmit.c')
| -rw-r--r-- | dnsstub/dns_transmit.c | 436 |
1 files changed, 436 insertions, 0 deletions
diff --git a/dnsstub/dns_transmit.c b/dnsstub/dns_transmit.c new file mode 100644 index 0000000..2513565 --- /dev/null +++ b/dnsstub/dns_transmit.c @@ -0,0 +1,436 @@ +#include <sys/types.h> +#include <sys/socket.h> +#include <unistd.h> +#include "socket_if.h" +#include "alloc.h" +#include "error.h" +#include "byte.h" +#include "uint_t.h" +#include "ip.h" +#include "dnsresolv.h" + +/** + @file dns_transmit.c + @authors djb, fefe, feh + @source qlibs + @brief DNS query function + @brief scope_ids[32] -> 32 LLU root servers supported +*/ + +#define DNSPORT 53 + +uint32 scope_ids[QUERY_MAXNS]; + +static const int timeouts[5] = { 1, 2, 4, 8, 16 }; /* quadratic, not exponentially */ + +int getscopeid(const struct dns_transmit *d,const char *ip) +{ + int i; + + if (byte_diff(ip,2,V6linklocal)) return 0; + for (i = 0; i < QUERY_MAXNS; ++i) + if (byte_equal(d->servers + 16 * i,16,ip)) + return scope_ids[i]; + + return 0; +} + +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; +} + +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 = EAGAIN; return 1; } + + return 0; +} + +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; +} + +void packetfree(struct dns_transmit *d) +{ + if (!d->packet) return; + alloc_free(d->packet); + d->packet = 0; +} + +void queryfree(struct dns_transmit *d) +{ + if (!d->query) return; + alloc_free(d->query); + d->query = 0; +} + +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); +} + +int randombind6(struct dns_transmit *d) +{ + int j; + + for (j = 0; j < 10; ++j) { + if (socket_bind6(d->s1 - 1,d->localip,1025 + dns_random(64510),d->scope_id) == 0) + return 0; + } + if (socket_bind6(d->s1 - 1,d->localip,0,d->scope_id) == 0) + return 0; + + return DNS_COM; +} + +int randombind4(struct dns_transmit *d) +{ + int j; + + for (j = 0; j < 10; ++j) { + if (socket_bind4(d->s1 - 1,d->localip + 12,1025 + dns_random(64510)) == 0) + return 0; + } + if (socket_bind4(d->s1 - 1,d->localip + 12,0) == 0) + return 0; + + return DNS_COM; +} + +int thisudp(struct dns_transmit *d) +{ + const char *ip; + + socketfree(d); + + while (d->udploop < 5) { + for (; d->curserver < QUERY_MAXNS; ++d->curserver) { + ip = d->servers + 16 * d->curserver; + if (byte_diff(ip,16,V6localnet)) { + d->query[2] = dns_random(256); + d->query[3] = dns_random(256); + + if (ip6_isv4mapped(ip)) { + d->s1 = 1 + socket_udp4(); + if (!d->s1) { dns_transmit_free(d); return DNS_COM; } + if (randombind4(d) < 0) { dns_transmit_free(d); return DNS_COM; } + } else { + d->s1 = 1 + socket_udp6(); + if (!d->s1) { dns_transmit_free(d); return DNS_COM; } + if (randombind6(d) < 0) { dns_transmit_free(d); return DNS_COM; } + } + + if (byte_equal(ip,2,V6linklocal) && !d->scope_id) + d->scope_id = getscopeid(d,ip); + if (socket_connect(d->s1 - 1,ip,DNSPORT,d->scope_id) == 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 DNS_COM; +} + +int firstudp(struct dns_transmit *d) +{ + d->curserver = 0; + return thisudp(d); +} + +int nextudp(struct dns_transmit *d) +{ + ++d->curserver; + return thisudp(d); +} + +int thistcp(struct dns_transmit *d) +{ + struct taia now; + const char *ip; + + socketfree(d); + packetfree(d); + + for (; d->curserver < QUERY_MAXNS; ++d->curserver) { + ip = d->servers + 16 * d->curserver; + if (byte_diff(ip,16,V6localnet)) { + d->query[2] = dns_random(256); + d->query[3] = dns_random(256); + + if (ip6_isv4mapped(ip)) { + d->s1 = 1 + socket_tcp4(); + if (!d->s1) { dns_transmit_free(d); return DNS_COM; } + if (randombind4(d) < 0) { dns_transmit_free(d); return DNS_COM; } + } else { + d->s1 = 1 + socket_tcp6(); + if (!d->s1) { dns_transmit_free(d); return DNS_COM; } + if (randombind6(d) < 0) { dns_transmit_free(d); return DNS_COM; } + } + + taia_now(&now); + taia_uint(&d->deadline,10); + taia_add(&d->deadline,&d->deadline,&now); + + if (byte_equal(ip,2,V6linklocal) && !d->scope_id) + d->scope_id = getscopeid(d,ip); + if (socket_connect(d->s1 - 1,ip,DNSPORT,d->scope_id) == 0) { + d->tcpstate = 2; + return 0; + } + if ((errno == EINPROGRESS) || (errno == EWOULDBLOCK)) { + d->tcpstate = 1; + return 0; + } + + socketfree(d); + } + } + + dns_transmit_free(d); + return DNS_COM; +} + +int firsttcp(struct dns_transmit *d) +{ + d->curserver = 0; + return thistcp(d); +} + +int nexttcp(struct dns_transmit *d) +{ + ++d->curserver; + return thistcp(d); +} + +int dns_transmit_start(struct dns_transmit *d,const char servers[QUERY_MAXIPLEN], \ + int flagrecursive,const char *q,const char qtype[2],const char localip[16]) +{ + unsigned int len; + + dns_transmit_free(d); + errno = EIO; + + len = dns_domain_length(q); + d->querylen = len + 18; + d->query = alloc(d->querylen); + if (!d->query) return DNS_COM; + + 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,(char *) qtype); + d->servers = servers; + byte_copy(d->localip,16,(char *) localip); + + d->udploop = flagrecursive ? 1 : 0; + + if (len + 16 > MSGSIZE) return firsttcp(d); + return firstudp(d); +} + +int dns_transmit_start6(struct dns_transmit *d,const char servers[QUERY_MAXIPLEN], \ + int flagrecursive,const char *q,const char qtype[2], \ + const char localip[16],const uint32 scopes[QUERY_MAXNS]) +{ + byte_copy(scope_ids,128,(char *) scopes); + + return dns_transmit_start(d,servers,flagrecursive,q,qtype,localip); +} + +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[MSGSIZE + 1]; + unsigned char ch; + int r; + int fd; + + errno = EIO; + fd = d->s1 - 1; + + if (!x->revents) { + if (taia_less((struct taia *)when,&d->deadline)) return 0; + errno = ETIMEDOUT; + if (d->tcpstate == 0) return nextudp(d); + return nexttcp(d); + } + +/* +have attempted to send UDP query to each server udploop times +have sent query to curserver on UDP socket s +*/ + if (d->tcpstate == 0) { + r = recv(fd,udpbuf,sizeof(udpbuf),0); + if (r <= 0) { + if (errno == ECONNREFUSED) 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 DNS_COM; } + byte_copy(d->packet,d->packetlen,udpbuf); + queryfree(d); + return 1; + } + +/* +have sent connection attempt to curserver on TCP socket s +pos not defined +*/ + if (d->tcpstate == 1) { + if (!socket_connected(fd)) return nexttcp(d); + d->pos = 0; + d->tcpstate = 2; + return 0; + } + +/* +have connection to curserver on TCP socket s +have sent pos bytes of query +*/ + if (d->tcpstate == 2) { + 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; + } + +/* +have sent entire query to curserver on TCP socket s +pos not defined +*/ + if (d->tcpstate == 3) { + r = read(fd,&ch,1); + if (r <= 0) return nexttcp(d); + d->packetlen = ch; + d->tcpstate = 4; + return 0; + } + +/* +have sent entire query to curserver on TCP socket s +pos not defined +have received one byte of packet length into packetlen +*/ + if (d->tcpstate == 4) { + 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 DNS_COM; } + return 0; + } + +/* +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 +*/ + if (d->tcpstate == 5) { + 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; +} |