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/*-------------------------------------------------------*/
/* lib/dns_smtp.c ( NTHU CS MapleBBS Ver 3.00 ) */
/*-------------------------------------------------------*/
/* target : included C file for DNS routines */
/* create : 96/11/20 */
/* update : 96/12/15 */
/*-------------------------------------------------------*/
#include "dns.h"
/* static inline */ void /* Thor. 990811: for bmtad use to check from */
dns_mx(domain, mxlist)
char *domain;
char *mxlist;
{
querybuf ans;
int n, ancount, qdcount;
unsigned char *cp, *eom;
int type;
*mxlist = 0;
n = dns_query(domain, T_MX, &ans);
if (n < 0)
return;
/* find first satisfactory answer */
cp = (u_char *) & ans + sizeof(HEADER);
eom = (u_char *) & ans + n;
for (qdcount = ntohs(ans.hdr.qdcount); qdcount--; cp += n + QFIXEDSZ)
{
if ((n = dn_skipname(cp, eom)) < 0)
return;
}
ancount = ntohs(ans.hdr.ancount);
domain = mxlist + MAX_MXLIST - MAX_DNAME - 2;
while (--ancount >= 0 && cp < eom)
{
if ((n = dn_expand((void *) &ans, eom, cp, mxlist, MAX_DNAME)) < 0)
break;
cp += n;
type = getshort(cp);
n = getshort(cp + 8);
cp += 10;
if (type == T_MX)
{
/* pref = getshort(cp); */
*mxlist = '\0';
if ((dn_expand((void *) &ans, eom, cp + 2, mxlist, MAX_DNAME)) < 0)
break;
if (!*mxlist)
return;
/* Thor.980820:註解: 將數個 MX entry 用 : 串起來以便一個一個試 */
while (*mxlist)
mxlist++;
*mxlist++ = ':';
if (mxlist >= domain)
break;
}
cp += n;
}
*mxlist = '\0';
}
int
dns_smtp(host)
char *host;
{
int sock;
char *str, *ptr, mxlist[MAX_MXLIST];
#ifdef HAVE_RELAY_SERVER
/* 如果有自定的 relay server，先 try 它試試 */
if ((sock = dns_open(RELAY_SERVER, 25)) >= 0)
return sock;
#endif
dns_mx(host, str = mxlist);
if (!*str)
{
/* Thor.990716: 因呼叫時可能將host用ip放入，故作特別處理，
使不透過dns_open()寄信 */
/* if(*host>='0' && *host<='9') return -1; */
/* Thor.990811: 用dns_aton()較完整 */
if (dns_aton(host) != INADDR_NONE)
return -1;
str = host;
}
for (;;)
{ /* Thor.980820: 註解: 萬一host格式為 xxx:yyy:zzz, 則先試 xxx,不行再試 yyy */
ptr = str;
while (sock = *ptr)
{
if (sock == ':')
{
*ptr++ = '\0';
break;
}
ptr++;
}
if (!*str)
return -1;
sock = dns_open(str, 25);
if (sock >= 0)
return sock;
str = ptr;
}
}
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