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#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <fcntl.h>
#include <arpa/inet.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <resolv.h>
#include <net/if.h>
#include "dietfeatures.h"
int __dns_fd=-1;
#ifdef WANT_IPV6_DNS
int __dns_fd6=-1;
#endif
/* the ad-hoc internal API from hell ;-) */
void __dns_make_fd(void);
void __dns_make_fd6(void);
void __dns_readstartfiles(void);
int __dns_decodename(unsigned char *packet,unsigned int offset,unsigned char *dest,
unsigned int maxlen,unsigned char* behindpacket);
void __dns_make_fd(void) {
int tmp;
struct sockaddr_in si;
if (__dns_fd>=0) return;
tmp=socket(PF_INET,SOCK_DGRAM,IPPROTO_UDP);
if (tmp<0) return;
si.sin_family=AF_INET;
si.sin_port=0;
si.sin_addr.s_addr=INADDR_ANY;
if (bind(tmp,(struct sockaddr*)&si,sizeof(si))) return;
__dns_fd=tmp;
}
#ifdef WANT_IPV6_DNS
void __dns_make_fd6(void) {
int tmp;
struct sockaddr_in6 si;
if (__dns_fd6>=0) return;
tmp=socket(PF_INET6,SOCK_DGRAM,IPPROTO_UDP);
if (tmp<0) return;
si.sin6_family=AF_INET6;
si.sin6_port=0;
memset(&si.sin6_addr,0,16);
if (bind(tmp,(struct sockaddr*)&si,sizeof(si))) return;
__dns_fd6=tmp;
}
#endif
static int parsesockaddr(const char* c,void* x) {
struct sockaddr_in to;
if (inet_aton(c,&to.sin_addr)) {
to.sin_port=htons(53);
to.sin_family=AF_INET;
memmove(x,&to,sizeof(struct sockaddr_in_pad));
return 1;
#ifdef WANT_IPV6_DNS
} else {
struct sockaddr_in6 to6;
char* d=strchr(c,'%');
to6.sin6_flowinfo=to6.sin6_scope_id=0;
if (d)
to6.sin6_scope_id=if_nametoindex(d+1);
if (inet_pton(AF_INET6,c,&to6.sin6_addr)) {
to6.sin6_port=htons(53);
to6.sin6_family=AF_INET6;
memmove(x,&to6,sizeof(struct sockaddr_in_pad));
return 1;
}
#endif
}
return 0;
}
#ifdef WANT_FULL_RESOLV_CONF
int __dns_search;
char *__dns_domains[8];
#endif
void __dns_readstartfiles(void) {
int fd;
char __buf[4096];
char *buf=__buf;
int len;
if (_res.nscount>0) return;
{
struct sockaddr_in to;
#ifdef WANT_IPV6_DNS
struct sockaddr_in6 to6;
#endif
char *cacheip=getenv("DNSCACHEIP");
#ifdef WANT_FULL_RESOLV_CONF
__dns_search=0;
#endif
if (cacheip)
if (parsesockaddr(cacheip,_res.nsaddr_list))
++_res.nscount;
}
_res.options=RES_RECURSE;
if ((fd=open("/etc/resolv.conf",O_RDONLY))<0) return;
len=read(fd,buf,4096);
close(fd);
{
char *last=buf+len;
for (; buf<last;) {
if (!strncmp(buf,"nameserver",10)) {
buf+=10;
while (buf<last && *buf!='\n') {
while (buf<last && isblank(*buf)) ++buf;
{
char *tmp=buf;
struct sockaddr_in i;
char save;
while (buf<last && !isspace(*buf)) ++buf;
if (buf>=last) break;
save=*buf;
*buf=0;
if (parsesockaddr(tmp,&_res.nsaddr_list[_res.nscount]))
if (_res.nscount<MAXNS) ++_res.nscount;
*buf=save;
}
}
}
#ifdef WANT_FULL_RESOLV_CONF
else if (!strncmp(buf,"search",6) || !strncmp(buf,"domain",6)) {
buf+=6;
while (buf<last && *buf!='\n') {
char save;
while (buf<last && (*buf==',' || isblank(*buf))) ++buf;
__dns_domains[__dns_search]=buf;
while (buf<last && (*buf=='.' || *buf=='-' || isalnum(*buf))) ++buf;
save=*buf;
if (buf<last) *buf=0;
if (__dns_domains[__dns_search]<buf &&
(__dns_domains[__dns_search]=strdup(__dns_domains[__dns_search])))
++__dns_search;
if (buf<last) *buf=save;
}
continue;
}
#endif
while (buf<last && *buf!='\n') ++buf;
while (buf<last && *buf=='\n') ++buf;
}
}
}
/* return length of decoded data or -1 */
int __dns_decodename(unsigned char *packet,unsigned int offset,unsigned char *dest,
unsigned int maxlen,unsigned char* behindpacket) {
unsigned char *tmp;
unsigned char *max=dest+maxlen;
unsigned char *after=packet+offset;
int ok=0;
for (tmp=after; maxlen>0&&*tmp; ) {
if (tmp>=behindpacket) return -1;
if ((*tmp>>6)==3) { /* goofy DNS decompression */
unsigned int ofs=((unsigned int)(*tmp&0x3f)<<8)|*(tmp+1);
if (ofs>=(unsigned int)offset) return -1; /* RFC1035: "pointer to a _prior_ occurrance" */
if (after<tmp+2) after=tmp+2;
tmp=packet+ofs;
ok=0;
} else {
unsigned int duh;
if (dest+*tmp+1>max) return -1;
if (tmp+*tmp+1>=behindpacket) return -1;
for (duh=*tmp; duh>0; --duh)
*dest++=*++tmp;
*dest++='.'; ok=1;
++tmp;
if (tmp>after) { after=tmp; if (!*tmp) ++after; }
}
}
if (ok) --dest;
*dest=0;
return after-packet;
}
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