#include "byte.h"

#include "case.h"

#include "env.h"

#include "buffer.h"

#include "strerr.h"

#include "ip4.h"

#include "uint16.h"

#include "ndelay.h"

#include "socket.h"

#include "droproot.h"

#include "qlog.h"

#include "response.h"

#include "dns.h"

extern char *fatal;

extern char *starting;

extern int respond(char *,char *,char *);

extern void initialize(void);

static char ip[4];

static uint16 port;

static char buf[513];

static int len;

static char *q;

static int doit(void)

{

unsigned int pos;

char header[12];

char qtype[2];

char qclass[2];

if (len >= sizeof buf) goto NOQ;

pos = dns_packet_copy(buf,len,0,header,12); if (!pos) goto NOQ;

if (header[2] & 128) goto NOQ;

if (header[4]) goto NOQ;

if (header[5] != 1) goto NOQ;

pos = dns_packet_getname(buf,len,pos,&q); if (!pos) goto NOQ;

pos = dns_packet_copy(buf,len,pos,qtype,2); if (!pos) goto NOQ;

pos = dns_packet_copy(buf,len,pos,qclass,2); if (!pos) goto NOQ;

if (!response_query(q,qtype,qclass)) goto NOQ;

response_id(header);

if (byte_equal(qclass,2,DNS_C_IN))

response[2] |= 4;

else

if (byte_diff(qclass,2,DNS_C_ANY)) goto WEIRDCLASS;

response[3] &= ~128;

if (!(header[2] & 1)) response[2] &= ~1;

if (header[2] & 126) goto NOTIMP;

if (byte_equal(qtype,2,DNS_T_AXFR)) goto NOTIMP;

case_lowerb(q,dns_domain_length(q));

if (!respond(q,qtype,ip)) {

qlog(ip,port,header,q,qtype," - ");

return 0;

}

qlog(ip,port,header,q,qtype," + ");

return 1;

NOTIMP:

response[3] &= ~15;

response[3] |= 4;

qlog(ip,port,header,q,qtype," I ");

return 1;

WEIRDCLASS:

response[3] &= ~15;

response[3] |= 1;

qlog(ip,port,header,q,qtype," C ");

return 1;

NOQ:

qlog(ip,port,"\0\0","","\0\0"," / ");

return 0;

}

int main()

{

char *x;

int udp53;

x = env_get("IP");

if (!x)

strerr_die2x(111,fatal,"$IP not set");

if (!ip4_scan(x,ip))

strerr_die3x(111,fatal,"unable to parse IP address ",x);

udp53 = socket_udp();

if (udp53 == -1)

strerr_die2sys(111,fatal,"unable to create UDP socket: ");

if (socket_bind4_reuse(udp53,ip,53) == -1)

strerr_die2sys(111,fatal,"unable to bind UDP socket: ");

droproot(fatal);

initialize();

ndelay_off(udp53);

socket_tryreservein(udp53,65536);

buffer_putsflush(buffer_2,starting);

for (;;) {

len = socket_recv4(udp53,buf,sizeof buf,ip,&port);

if (len < 0) continue;

if (!doit()) continue;

if (response_len > 512) response_tc();

socket_send4(udp53,response,response_len,ip,port);

/* may block for buffer space; if it fails, too bad */

}

}