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-rw-r--r--response.c121
1 files changed, 121 insertions, 0 deletions
diff --git a/response.c b/response.c
new file mode 100644
index 0000000..ba90c89
--- /dev/null
+++ b/response.c
@@ -0,0 +1,121 @@
+#include "dns.h"
+#include "byte.h"
+#include "uint16.h"
+#include "response.h"
+
+char response[65535];
+unsigned int response_len = 0; /* <= 65535 */
+static unsigned int tctarget;
+
+#define NAMES 100
+static char name[NAMES][128];
+static unsigned int name_ptr[NAMES]; /* each < 16384 */
+static unsigned int name_num;
+
+int response_addbytes(const char *buf,unsigned int len)
+{
+ if (len > 65535 - response_len) return 0;
+ byte_copy(response + response_len,len,buf);
+ response_len += len;
+ return 1;
+}
+
+int response_addname(const char *d)
+{
+ unsigned int dlen;
+ unsigned int i;
+ char buf[2];
+
+ dlen = dns_domain_length(d);
+
+ while (*d) {
+ for (i = 0;i < name_num;++i)
+ if (dns_domain_equal(d,name[i])) {
+ uint16_pack_big(buf,49152 + name_ptr[i]);
+ return response_addbytes(buf,2);
+ }
+ if (dlen <= 128)
+ if (name_num < NAMES) {
+ byte_copy(name[name_num],dlen,d);
+ name_ptr[name_num] = response_len;
+ ++name_num;
+ }
+ i = (unsigned char) *d;
+ ++i;
+ if (!response_addbytes(d,i)) return 0;
+ d += i;
+ dlen -= i;
+ }
+ return response_addbytes(d,1);
+}
+
+int response_query(const char *q,const char qtype[2],const char qclass[2])
+{
+ response_len = 0;
+ name_num = 0;
+ if (!response_addbytes("\0\0\201\200\0\1\0\0\0\0\0\0",12)) return 0;
+ if (!response_addname(q)) return 0;
+ if (!response_addbytes(qtype,2)) return 0;
+ if (!response_addbytes(qclass,2)) return 0;
+ tctarget = response_len;
+ return 1;
+}
+
+static unsigned int dpos;
+
+static int flaghidettl = 0;
+
+void response_hidettl(void)
+{
+ flaghidettl = 1;
+}
+
+int response_rstart(const char *d,const char type[2],uint32 ttl)
+{
+ char ttlstr[4];
+ if (!response_addname(d)) return 0;
+ if (!response_addbytes(type,2)) return 0;
+ if (!response_addbytes(DNS_C_IN,2)) return 0;
+ if (flaghidettl) ttl = 0;
+ uint32_pack_big(ttlstr,ttl);
+ if (!response_addbytes(ttlstr,4)) return 0;
+ if (!response_addbytes("\0\0",2)) return 0;
+ dpos = response_len;
+ return 1;
+}
+
+void response_rfinish(int x)
+{
+ uint16_pack_big(response + dpos - 2,response_len - dpos);
+ if (!++response[x + 1]) ++response[x];
+}
+
+int response_cname(const char *c,const char *d,uint32 ttl)
+{
+ if (!response_rstart(c,DNS_T_CNAME,ttl)) return 0;
+ if (!response_addname(d)) return 0;
+ response_rfinish(RESPONSE_ANSWER);
+ return 1;
+}
+
+void response_nxdomain(void)
+{
+ response[3] |= 3;
+ response[2] |= 4;
+}
+
+void response_servfail(void)
+{
+ response[3] |= 2;
+}
+
+void response_id(const char id[2])
+{
+ byte_copy(response,2,id);
+}
+
+void response_tc(void)
+{
+ response[2] |= 2;
+ response_len = tctarget;
+}