1 files changed, 116 insertions, 0 deletions
diff --git a/server.c b/server.c
new file mode 100644
index 0000000..e486fe1
--- /dev/null
+++ b/server.c
@@ -0,0 +1,116 @@
+#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 */
+  }
+}