-/* $Cambridge: exim/src/src/dns.c,v 1.7 2005/06/10 13:29:36 tom Exp $ */
+/* $Cambridge: exim/src/src/dns.c,v 1.17 2007/01/08 10:50:18 ph10 Exp $ */
/*************************************************
* Exim - an Internet mail transport agent *
*************************************************/
-/* Copyright (c) University of Cambridge 1995 - 2005 */
+/* Copyright (c) University of Cambridge 1995 - 2007 */
/* See the file NOTICE for conditions of use and distribution. */
/* Functions for interfacing with the DNS. */
#endif
+/*************************************************
+* Fake DNS resolver *
+*************************************************/
+
+/* This function is called instead of res_search() when Exim is running in its
+test harness. It recognizes some special domain names, and uses them to force
+failure and retry responses (optionally with a delay). Otherwise, it calls an
+external utility that mocks-up a nameserver, if it can find the utility.
+If not, it passes its arguments on to res_search(). The fake nameserver may
+also return a code specifying that the name should be passed on.
+
+Background: the original test suite required a real nameserver to carry the
+test zones, whereas the new test suit has the fake server for portability. This
+code supports both.
+
+Arguments:
+ domain the domain name
+ type the DNS record type
+ answerptr where to put the answer
+ size size of the answer area
+
+Returns: length of returned data, or -1 on error (h_errno set)
+*/
+
+static int
+fakens_search(uschar *domain, int type, uschar *answerptr, int size)
+{
+int len = Ustrlen(domain);
+int asize = size; /* Locally modified */
+uschar *endname;
+uschar name[256];
+uschar utilname[256];
+uschar *aptr = answerptr; /* Locally modified */
+struct stat statbuf;
+
+/* Remove terminating dot. */
+
+if (domain[len - 1] == '.') len--;
+Ustrncpy(name, domain, len);
+name[len] = 0;
+endname = name + len;
+
+/* This code, for forcing TRY_AGAIN and NO_RECOVERY, is here so that it works
+for the old test suite that uses a real nameserver. When the old test suite is
+eventually abandoned, this code could be moved into the fakens utility. */
+
+if (len >= 14 && Ustrcmp(endname - 14, "test.again.dns") == 0)
+ {
+ int delay = Uatoi(name); /* digits at the start of the name */
+ DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n",
+ name, dns_text_type(type));
+ if (delay > 0)
+ {
+ DEBUG(D_dns) debug_printf("delaying %d seconds\n", delay);
+ sleep(delay);
+ }
+ h_errno = TRY_AGAIN;
+ return -1;
+ }
+
+if (len >= 13 && Ustrcmp(endname - 13, "test.fail.dns") == 0)
+ {
+ DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n",
+ name, dns_text_type(type));
+ h_errno = NO_RECOVERY;
+ return -1;
+ }
+
+/* Look for the fakens utility, and if it exists, call it. */
+
+(void)string_format(utilname, sizeof(utilname), "%s/../bin/fakens",
+ spool_directory);
+
+if (stat(CS utilname, &statbuf) >= 0)
+ {
+ pid_t pid;
+ int infd, outfd, rc;
+ uschar *argv[5];
+
+ DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n",
+ name, dns_text_type(type));
+
+ argv[0] = utilname;
+ argv[1] = spool_directory;
+ argv[2] = name;
+ argv[3] = dns_text_type(type);
+ argv[4] = NULL;
+
+ pid = child_open(argv, NULL, 0000, &infd, &outfd, FALSE);
+ if (pid < 0)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "failed to run fakens: %s",
+ strerror(errno));
+
+ len = 0;
+ rc = -1;
+ while (asize > 0 && (rc = read(outfd, aptr, asize)) > 0)
+ {
+ len += rc;
+ aptr += rc; /* Don't modify the actual arguments, because they */
+ asize -= rc; /* may need to be passed on to res_search(). */
+ }
+
+ if (rc < 0)
+ log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s",
+ strerror(errno));
+
+ switch(child_close(pid, 0))
+ {
+ case 0: return len;
+ case 1: h_errno = HOST_NOT_FOUND; return -1;
+ case 2: h_errno = TRY_AGAIN; return -1;
+ default:
+ case 3: h_errno = NO_RECOVERY; return -1;
+ case 4: h_errno = NO_DATA; return -1;
+ case 5: /* Pass on to res_search() */
+ DEBUG(D_dns) debug_printf("fakens returned PASS_ON\n");
+ }
+ }
+
+/* fakens utility not found, or it returned "pass on" */
+
+DEBUG(D_dns) debug_printf("passing %s on to res_search()\n", domain);
+
+return res_search(CS domain, C_IN, type, answerptr, size);
+}
+
+
/*************************************************
* Initialize and configure resolver *
* Turn DNS type into text *
*************************************************/
-/* Turn the coded record type into a string for printing.
+/* Turn the coded record type into a string for printing. All those that Exim
+uses should be included here.
Argument: record type
Returns: pointer to string
case T_A6: return US"A6";
case T_TXT: return US"TXT";
case T_PTR: return US"PTR";
+ case T_SOA: return US"SOA";
case T_SRV: return US"SRV";
case T_NS: return US"NS";
case T_CNAME: return US"CNAME";
Returns: DNS_SUCCEED successful lookup
DNS_NOMATCH name not found (NXDOMAIN)
or name contains illegal characters (if checking)
+ or name is an IP address (for IP address lookup)
DNS_NODATA domain exists, but no data for this type (NODATA)
DNS_AGAIN soft failure, try again later
DNS_FAIL DNS failure
int
dns_basic_lookup(dns_answer *dnsa, uschar *name, int type)
{
+int rc = -1;
#ifndef STAND_ALONE
-int rc;
uschar *save;
#endif
return previous->data.val;
}
-/* If we are running in the test harness, recognize a couple of special
-names that always give error returns. This makes it straightforward to
-test the handling of DNS errors. */
-
-if (running_in_test_harness)
- {
- uschar *endname = name + Ustrlen(name);
- if (Ustrcmp(endname - 14, "test.again.dns") == 0)
- {
- int delay = Uatoi(name); /* digits at the start of the name */
- DEBUG(D_dns) debug_printf("Real DNS lookup of %s (%s) bypassed for testing\n",
- name, dns_text_type(type));
- if (delay > 0)
- {
- DEBUG(D_dns) debug_printf("delaying %d seconds\n", delay);
- sleep(delay);
- }
- DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
- return dns_return(name, type, DNS_AGAIN);
- }
- if (Ustrcmp(endname - 13, "test.fail.dns") == 0)
- {
- DEBUG(D_dns) debug_printf("Real DNS lookup of %s (%s) bypassed for testing\n",
- name, dns_text_type(type));
- DEBUG(D_dns) debug_printf("returning DNS_FAIL\n");
- return dns_return(name, type, DNS_FAIL);
- }
- }
-
/* If configured, check the hygene of the name passed to lookup. Otherwise,
although DNS lookups may give REFUSED at the lower level, some resolvers
turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
#endif /* STAND_ALONE */
/* Call the resolver; for an overlong response, res_search() will return the
-number of bytes the message would need, so we need to check for this case.
-The effect is to truncate overlong data. */
+number of bytes the message would need, so we need to check for this case. The
+effect is to truncate overlong data.
+
+On some systems, res_search() will recognize "A-for-A" queries and return
+the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some
+nameservers are also believed to do this. It is, of course, contrary to the
+specification of the DNS, so we lock it out. */
+
+if ((
+ #ifdef SUPPORT_A6
+ type == T_A6 ||
+ #endif
+ type == T_A || type == T_AAAA) &&
+ string_is_ip_address(name, NULL) != 0)
+ return DNS_NOMATCH;
+
+/* If we are running in the test harness, instead of calling the normal resolver
+(res_search), we call fakens_search(), which recognizes certain special
+domains, and interfaces to a fake nameserver for certain special zones. */
+
+if (running_in_test_harness)
+ dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET);
+else
+ dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET);
-dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET);
if (dnsa->answerlen > MAXPACKET) dnsa->answerlen = MAXPACKET;
if (dnsa->answerlen < 0) switch (h_errno)
contents of any rr blocks returned by dns_next_rr() as they use the same
area in the dnsa block. */
- DEBUG(D_dns) debug_printf("Back in dns_lookup()\n");
-
cname_rr.data = type_rr.data = NULL;
for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
rr != NULL;
else if (rr->type == T_CNAME) cname_rr = *rr;
}
- /* If a CNAME was found, take the fully qualified name from it; otherwise
- from the first data record, if present. For testing, there is a magic name
- that gets its casing adjusted, because my resolver doesn't seem to pass back
- upper case letters in domain names. */
+ /* For the first time round this loop, if a CNAME was found, take the fully
+ qualified name from it; otherwise from the first data record, if present. */
- if (fully_qualified_name != NULL)
+ if (i == 0 && fully_qualified_name != NULL)
{
if (cname_rr.data != NULL)
{
}
else if (type_rr.data != NULL)
{
- if (running_in_test_harness &&
- Ustrcmp(type_rr.name, "uppercase.test.ex") == 0)
- *fully_qualified_name = US"UpperCase.test.ex";
- else
- {
- if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 &&
- type_rr.name[0] != '*')
- *fully_qualified_name = string_copy_dnsdomain(type_rr.name);
- }
+ if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 &&
+ type_rr.name[0] != '*')
+ *fully_qualified_name = string_copy_dnsdomain(type_rr.name);
}
}
cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256);
if (datalen < 0) return DNS_FAIL;
name = data;
+
+ DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name);
} /* Loop back to do another lookup */
/*Control reaches here after 10 times round the CNAME loop. Something isn't
git://git.exim.org / users / jgh / exim.git / blobdiff