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-rw-r--r--dns.c398
1 files changed, 398 insertions, 0 deletions
diff --git a/dns.c b/dns.c
new file mode 100644
index 0000000..e9faad7
--- /dev/null
+++ b/dns.c
@@ -0,0 +1,398 @@
+#include <stdio.h>
+#include <netdb.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <errno.h>
+extern int res_query();
+extern int res_search();
+#include "ip.h"
+#include "ipalloc.h"
+#include "fmt.h"
+#include "alloc.h"
+#include "str.h"
+#include "stralloc.h"
+#include "dns.h"
+#include "case.h"
+
+static unsigned short getshort(c) unsigned char *c;
+{ unsigned short u; u = c[0]; return (u << 8) + c[1]; }
+
+static union { HEADER hdr; unsigned char buf[PACKETSZ]; } response;
+static int responselen;
+static unsigned char *responseend;
+static unsigned char *responsepos;
+
+static int numanswers;
+static char name[MAXDNAME];
+static struct ip_address ip;
+unsigned short pref;
+
+static stralloc glue = {0};
+
+static int (*lookup)() = res_query;
+
+static int resolve(domain,type)
+stralloc *domain;
+int type;
+{
+ int n;
+ int i;
+
+ errno = 0;
+ if (!stralloc_copy(&glue,domain)) return DNS_MEM;
+ if (!stralloc_0(&glue)) return DNS_MEM;
+ responselen = lookup(glue.s,C_IN,type,response.buf,sizeof(response));
+ if (responselen <= 0)
+ {
+ if (errno == ECONNREFUSED) return DNS_SOFT;
+ if (h_errno == TRY_AGAIN) return DNS_SOFT;
+ return DNS_HARD;
+ }
+ if (responselen >= sizeof(response))
+ responselen = sizeof(response);
+ responseend = response.buf + responselen;
+ responsepos = response.buf + sizeof(HEADER);
+ n = ntohs(response.hdr.qdcount);
+ while (n-- > 0)
+ {
+ i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
+ if (i < 0) return DNS_SOFT;
+ responsepos += i;
+ i = responseend - responsepos;
+ if (i < QFIXEDSZ) return DNS_SOFT;
+ responsepos += QFIXEDSZ;
+ }
+ numanswers = ntohs(response.hdr.ancount);
+ return 0;
+}
+
+static int findname(wanttype)
+int wanttype;
+{
+ unsigned short rrtype;
+ unsigned short rrdlen;
+ int i;
+
+ if (numanswers <= 0) return 2;
+ --numanswers;
+ if (responsepos == responseend) return DNS_SOFT;
+
+ i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
+ if (i < 0) return DNS_SOFT;
+ responsepos += i;
+
+ i = responseend - responsepos;
+ if (i < 4 + 3 * 2) return DNS_SOFT;
+
+ rrtype = getshort(responsepos);
+ rrdlen = getshort(responsepos + 8);
+ responsepos += 10;
+
+ if (rrtype == wanttype)
+ {
+ if (dn_expand(response.buf,responseend,responsepos,name,MAXDNAME) < 0)
+ return DNS_SOFT;
+ responsepos += rrdlen;
+ return 1;
+ }
+
+ responsepos += rrdlen;
+ return 0;
+}
+
+static int findip(wanttype)
+int wanttype;
+{
+ unsigned short rrtype;
+ unsigned short rrdlen;
+ int i;
+
+ if (numanswers <= 0) return 2;
+ --numanswers;
+ if (responsepos == responseend) return DNS_SOFT;
+
+ i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
+ if (i < 0) return DNS_SOFT;
+ responsepos += i;
+
+ i = responseend - responsepos;
+ if (i < 4 + 3 * 2) return DNS_SOFT;
+
+ rrtype = getshort(responsepos);
+ rrdlen = getshort(responsepos + 8);
+ responsepos += 10;
+
+ if (rrtype == wanttype)
+ {
+ if (rrdlen < 4)
+ return DNS_SOFT;
+ ip.d[0] = responsepos[0];
+ ip.d[1] = responsepos[1];
+ ip.d[2] = responsepos[2];
+ ip.d[3] = responsepos[3];
+ responsepos += rrdlen;
+ return 1;
+ }
+
+ responsepos += rrdlen;
+ return 0;
+}
+
+static int findmx(wanttype)
+int wanttype;
+{
+ unsigned short rrtype;
+ unsigned short rrdlen;
+ int i;
+
+ if (numanswers <= 0) return 2;
+ --numanswers;
+ if (responsepos == responseend) return DNS_SOFT;
+
+ i = dn_expand(response.buf,responseend,responsepos,name,MAXDNAME);
+ if (i < 0) return DNS_SOFT;
+ responsepos += i;
+
+ i = responseend - responsepos;
+ if (i < 4 + 3 * 2) return DNS_SOFT;
+
+ rrtype = getshort(responsepos);
+ rrdlen = getshort(responsepos + 8);
+ responsepos += 10;
+
+ if (rrtype == wanttype)
+ {
+ if (rrdlen < 3)
+ return DNS_SOFT;
+ pref = (responsepos[0] << 8) + responsepos[1];
+ if (dn_expand(response.buf,responseend,responsepos + 2,name,MAXDNAME) < 0)
+ return DNS_SOFT;
+ responsepos += rrdlen;
+ return 1;
+ }
+
+ responsepos += rrdlen;
+ return 0;
+}
+
+void dns_init(flagsearch)
+int flagsearch;
+{
+ res_init();
+ if (flagsearch) lookup = res_search;
+}
+
+int dns_cname(sa)
+stralloc *sa;
+{
+ int r;
+ int loop;
+ for (loop = 0;loop < 10;++loop)
+ {
+ if (!sa->len) return loop;
+ if (sa->s[sa->len - 1] == ']') return loop;
+ if (sa->s[sa->len - 1] == '.') { --sa->len; continue; }
+ switch(resolve(sa,T_ANY))
+ {
+ case DNS_MEM: return DNS_MEM;
+ case DNS_SOFT: return DNS_SOFT;
+ case DNS_HARD: return loop;
+ default:
+ while ((r = findname(T_CNAME)) != 2)
+ {
+ if (r == DNS_SOFT) return DNS_SOFT;
+ if (r == 1)
+ {
+ if (!stralloc_copys(sa,name)) return DNS_MEM;
+ break;
+ }
+ }
+ if (r == 2) return loop;
+ }
+ }
+ return DNS_HARD; /* alias loop */
+}
+
+#define FMT_IAA 40
+
+static int iaafmt(s,ip)
+char *s;
+struct ip_address *ip;
+{
+ unsigned int i;
+ unsigned int len;
+ len = 0;
+ i = fmt_ulong(s,(unsigned long) ip->d[3]); len += i; if (s) s += i;
+ i = fmt_str(s,"."); len += i; if (s) s += i;
+ i = fmt_ulong(s,(unsigned long) ip->d[2]); len += i; if (s) s += i;
+ i = fmt_str(s,"."); len += i; if (s) s += i;
+ i = fmt_ulong(s,(unsigned long) ip->d[1]); len += i; if (s) s += i;
+ i = fmt_str(s,"."); len += i; if (s) s += i;
+ i = fmt_ulong(s,(unsigned long) ip->d[0]); len += i; if (s) s += i;
+ i = fmt_str(s,".in-addr.arpa."); len += i; if (s) s += i;
+ return len;
+}
+
+int dns_ptr(sa,ip)
+stralloc *sa;
+struct ip_address *ip;
+{
+ int r;
+
+ if (!stralloc_ready(sa,iaafmt((char *) 0,ip))) return DNS_MEM;
+ sa->len = iaafmt(sa->s,ip);
+ switch(resolve(sa,T_PTR))
+ {
+ case DNS_MEM: return DNS_MEM;
+ case DNS_SOFT: return DNS_SOFT;
+ case DNS_HARD: return DNS_HARD;
+ }
+ while ((r = findname(T_PTR)) != 2)
+ {
+ if (r == DNS_SOFT) return DNS_SOFT;
+ if (r == 1)
+ {
+ if (!stralloc_copys(sa,name)) return DNS_MEM;
+ return 0;
+ }
+ }
+ return DNS_HARD;
+}
+
+static int dns_ipplus(ia,sa,pref)
+ipalloc *ia;
+stralloc *sa;
+int pref;
+{
+ int r;
+ struct ip_mx ix;
+
+ if (!stralloc_copy(&glue,sa)) return DNS_MEM;
+ if (!stralloc_0(&glue)) return DNS_MEM;
+ if (glue.s[0]) {
+ ix.pref = 0;
+ if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)])
+ {
+ if (!ipalloc_append(ia,&ix)) return DNS_MEM;
+ return 0;
+ }
+ }
+
+ switch(resolve(sa,T_A))
+ {
+ case DNS_MEM: return DNS_MEM;
+ case DNS_SOFT: return DNS_SOFT;
+ case DNS_HARD: return DNS_HARD;
+ }
+ while ((r = findip(T_A)) != 2)
+ {
+ ix.ip = ip;
+ ix.pref = pref;
+ if (r == DNS_SOFT) return DNS_SOFT;
+ if (r == 1)
+ if (!ipalloc_append(ia,&ix)) return DNS_MEM;
+ }
+ return 0;
+}
+
+int dns_ip(ia,sa)
+ipalloc *ia;
+stralloc *sa;
+{
+ if (!ipalloc_readyplus(ia,0)) return DNS_MEM;
+ ia->len = 0;
+ return dns_ipplus(ia,sa,0);
+}
+
+int dns_mxip(ia,sa,random)
+ipalloc *ia;
+stralloc *sa;
+unsigned long random;
+{
+ int r;
+ struct mx { stralloc sa; unsigned short p; } *mx;
+ struct ip_mx ix;
+ int nummx;
+ int i;
+ int j;
+ int flagsoft;
+
+ if (!ipalloc_readyplus(ia,0)) return DNS_MEM;
+ ia->len = 0;
+
+ if (!stralloc_copy(&glue,sa)) return DNS_MEM;
+ if (!stralloc_0(&glue)) return DNS_MEM;
+ if (glue.s[0]) {
+ ix.pref = 0;
+ if (!glue.s[ip_scan(glue.s,&ix.ip)] || !glue.s[ip_scanbracket(glue.s,&ix.ip)])
+ {
+ if (!ipalloc_append(ia,&ix)) return DNS_MEM;
+ return 0;
+ }
+ }
+
+ switch(resolve(sa,T_MX))
+ {
+ case DNS_MEM: return DNS_MEM;
+ case DNS_SOFT: return DNS_SOFT;
+ case DNS_HARD: return dns_ip(ia,sa);
+ }
+
+ mx = (struct mx *) alloc(numanswers * sizeof(struct mx));
+ if (!mx) return DNS_MEM;
+ nummx = 0;
+
+ while ((r = findmx(T_MX)) != 2)
+ {
+ if (r == DNS_SOFT) { alloc_free(mx); return DNS_SOFT; }
+ if (r == 1)
+ {
+ mx[nummx].p = pref;
+ mx[nummx].sa.s = 0;
+ if (!stralloc_copys(&mx[nummx].sa,name))
+ {
+ while (nummx > 0) alloc_free(mx[--nummx].sa.s);
+ alloc_free(mx); return DNS_MEM;
+ }
+ ++nummx;
+ }
+ }
+
+ if (!nummx) return dns_ip(ia,sa); /* e.g., CNAME -> A */
+
+ flagsoft = 0;
+ while (nummx > 0)
+ {
+ unsigned long numsame;
+
+ i = 0;
+ numsame = 1;
+ for (j = 1;j < nummx;++j)
+ if (mx[j].p < mx[i].p)
+ {
+ i = j;
+ numsame = 1;
+ }
+ else if (mx[j].p == mx[i].p)
+ {
+ ++numsame;
+ random = random * 69069 + 1;
+ if ((random / 2) < (2147483647 / numsame))
+ i = j;
+ }
+
+ switch(dns_ipplus(ia,&mx[i].sa,mx[i].p))
+ {
+ case DNS_MEM: case DNS_SOFT:
+ flagsoft = 1; break;
+ }
+
+ alloc_free(mx[i].sa.s);
+ mx[i] = mx[--nummx];
+ }
+
+ alloc_free(mx);
+ return flagsoft;
+}
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