2 * checkalias.c -- check to see if two hostnames or IP addresses are equivalent
4 * Copyright 1997 by Eric S. Raymond
5 * For license terms, see the file COPYING in this directory.
8 #ifdef HAVE_GETHOSTBYNAME
12 #include <sys/types.h>
13 #include <sys/socket.h>
14 #include <netinet/in.h>
15 #include <arpa/inet.h>
18 #include "fetchmail.h"
22 static int is_ip_alias(const char *name1,const char *name2)
24 * Given two hostnames as arguments, returns TRUE if they
25 * have at least one IP address in common.
26 * No check is done on errors returned by gethostbyname,
27 * the calling function does them.
30 typedef unsigned char address_t[sizeof (struct in_addr)];
31 typedef struct _address_e
33 struct _address_e *next;
37 address_e *host_a_addr=0, *host_b_addr=0; /* assignments pacify -Wall */
38 address_e *dummy_addr;
44 hp = gethostbyname(name1);
46 dummy_addr = (address_e *)NULL;
48 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
51 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
52 xalloca(host_a_addr, address_e *, sizeof (address_e));
53 memset (host_a_addr,0, sizeof (address_e));
54 host_a_addr->next = dummy_addr;
55 (void) memcpy(&host_a_addr->address, *p, sizeof (in.s_addr));
56 dummy_addr = host_a_addr;
59 hp = gethostbyname(name2);
61 dummy_addr = (address_e *)NULL;
62 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
65 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
66 xalloca(host_b_addr, address_e *, sizeof (address_e));
67 memset (host_b_addr,0, sizeof (address_e));
68 host_b_addr->next = dummy_addr;
69 (void) memcpy(&host_b_addr->address, *p, sizeof (in.s_addr));
70 dummy_addr = host_b_addr;
77 if (!memcmp(host_b_addr->address,host_a_addr->address, sizeof (address_t)))
80 host_b_addr = host_b_addr->next;
82 host_a_addr = host_a_addr->next;
87 int is_host_alias(const char *name, struct query *ctl)
88 /* determine whether name is a DNS alias of the mailserver for this query */
90 struct hostent *he,*he_st;
91 struct mxentry *mxp, *mxrecords;
93 struct hostdata *lead_server =
94 ctl->server.lead_server ? ctl->server.lead_server : &ctl->server;
97 * The first two checks are optimizations that will catch a good
100 * (1) check against the `true name' deduced from the poll label
101 * and the via option (if present) at the beginning of the poll cycle.
102 * Odds are good this will either be the mailserver's FQDN or a suffix of
103 * it with the mailserver's domain's default host name omitted.
105 * (2) Then check the rest of the `also known as'
106 * cache accumulated by previous DNS checks. This cache is primed
107 * by the aka list option.
109 * Any of these on a mail address is definitive. Only if the
110 * name doesn't match any is it time to call the bind library.
111 * If this happens odds are good we're looking at an MX name.
113 if (strcasecmp(lead_server->truename, name) == 0)
115 else if (str_in_list(&lead_server->akalist, name, TRUE))
117 else if (!ctl->server.dns)
120 #ifndef HAVE_RES_SEARCH
124 * The only code that calls the BIND library is here and in the
125 * start-of-run probe with gethostbyname(3) under ETRN/Kerberos.
127 * We know DNS service was up at the beginning of the run.
128 * If it's down, our nameserver has crashed. We don't want to try
129 * delivering the current message or anything else from the
130 * current server until it's back up.
132 else if ((he = gethostbyname(name)) != (struct hostent *)NULL)
134 if (strcasecmp(ctl->server.truename, he->h_name) == 0)
136 else if (((he_st = gethostbyname(ctl->server.truename)) != (struct hostent *)NULL) && ctl->server.checkalias)
138 if (outlevel >= O_DEBUG)
139 error(0, 0, "Checking if %s is really the same node as %s",ctl->server.truename,name);
140 if (is_ip_alias(ctl->server.truename,name) == TRUE)
142 if (outlevel >= O_DEBUG)
143 error(0, 0, "Yes, their IP addresses match");
146 if (outlevel >= O_DEBUG)
147 error(0, 0, "No, their IP addresses don't match");
155 case HOST_NOT_FOUND: /* specified host is unknown */
156 case NO_ADDRESS: /* valid, but does not have an IP address */
159 case NO_RECOVERY: /* non-recoverable name server error */
160 case TRY_AGAIN: /* temporary error on authoritative server */
162 if (outlevel != O_SILENT)
163 putchar('\n'); /* terminate the progress message */
165 "nameserver failure while looking for `%s' during poll of %s.",
166 name, ctl->server.pollname);
172 * We're only here if DNS was OK but the gethostbyname() failed
173 * with a HOST_NOT_FOUND or NO_ADDRESS error.
174 * Search for a name match on MX records pointing to the server.
177 if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
181 case HOST_NOT_FOUND: /* specified host is unknown */
182 case NO_ADDRESS: /* valid, but does not have an IP address */
186 case NO_RECOVERY: /* non-recoverable name server error */
187 case TRY_AGAIN: /* temporary error on authoritative server */
190 "nameserver failure while looking for `%s' during poll of %s.",
191 name, ctl->server.pollname);
198 for (mxp = mxrecords; mxp->name; mxp++)
199 if (strcasecmp(ctl->server.truename, mxp->name) == 0)
205 /* add this name to relevant server's `also known as' list */
206 save_str(&lead_server->akalist, name, 0);
208 #endif /* HAVE_RES_SEARCH */
210 #endif /* HAVE_GETHOSTBYNAME */
212 /* checkalias.c ends here */