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
11 #include <sys/types.h>
12 #include <sys/socket.h>
13 #include <netinet/in.h>
14 #include <arpa/inet.h>
17 #include "fetchmail.h"
21 static int is_ip_alias(const char *name1,const char *name2)
23 * Given two hostnames as arguments, returns TRUE if they
24 * have at least one IP address in common.
25 * It is meant to be called by the is_host_alias() function in driver.c
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, *host_b_addr,*dummy_addr;
43 hp = gethostbyname(name1);
45 dummy_addr = (address_e *)NULL;
47 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
50 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
51 host_a_addr = (address_e *)xmalloc(sizeof( address_e));
52 memset (host_a_addr,0, sizeof (address_e));
53 host_a_addr->next = dummy_addr;
54 (void) memcpy(&host_a_addr->address, *p, sizeof (in.s_addr));
55 dummy_addr = host_a_addr;
58 hp = gethostbyname(name2);
60 dummy_addr = (address_e *)NULL;
61 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
64 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
65 host_b_addr = (address_e *)xmalloc(sizeof( address_e));
66 memset (host_b_addr,0, sizeof (address_e));
67 host_b_addr->next = dummy_addr;
68 (void) memcpy(&host_b_addr->address, *p, sizeof (in.s_addr));
69 dummy_addr = host_b_addr;
76 if (!memcmp(host_b_addr->address,host_a_addr->address, sizeof (address_t)))
79 host_b_addr = host_b_addr->next;
81 host_a_addr = host_a_addr->next;
86 int is_host_alias(const char *name, struct query *ctl)
87 /* determine whether name is a DNS alias of the hostname */
89 struct hostent *he,*he_st;
90 struct mxentry *mxp, *mxrecords;
92 struct hostdata *lead_server =
93 ctl->server.lead_server ? ctl->server.lead_server : &ctl->server;
96 * The first two checks are optimizations that will catch a good
99 * (1) check against the `true name' deduced from the poll label
100 * and the via option (if present) at the beginning of the poll cycle.
101 * Odds are good this will either be the mailserver's FQDN or a suffix of
102 * it with the mailserver's domain's default host name omitted.
104 * (2) Then check the rest of the `also known as'
105 * cache accumulated by previous DNS checks. This cache is primed
106 * by the aka list option.
108 * Any of these on a mail address is definitive. Only if the
109 * name doesn't match any is it time to call the bind library.
110 * If this happens odds are good we're looking at an MX name.
112 if (strcasecmp(lead_server->truename, name) == 0)
114 else if (str_in_list(&lead_server->akalist, name, TRUE))
116 else if (!ctl->server.dns)
119 #ifndef HAVE_RES_SEARCH
123 * The only code that calls the BIND library is here and in the
124 * start-of-query probe with gethostbyname(3).
126 * We know DNS service was up at the beginning of this poll cycle.
127 * If it's down, our nameserver has crashed. We don't want to try
128 * delivering the current message or anything else from this
129 * mailbox until it's back up.
131 else if ((he = gethostbyname(name)) != (struct hostent *)NULL)
133 if (strcasecmp(ctl->server.truename, he->h_name) == 0)
135 else if (((he_st = gethostbyname(ctl->server.truename)) != (struct hostent *)NULL) && ctl->server.checkalias)
137 if (outlevel == O_VERBOSE)
138 error(0, 0, "Checking if %s is really the same node as %s",ctl->server.truename,name);
139 if (is_ip_alias(ctl->server.truename,name) == TRUE)
141 if (outlevel == O_VERBOSE)
142 error(0, 0, "Yes, their IP addresses match");
145 if (outlevel == O_VERBOSE)
146 error(0, 0, "No, their IP addresses don't match");
154 case HOST_NOT_FOUND: /* specified host is unknown */
155 case NO_ADDRESS: /* valid, but does not have an IP address */
158 case NO_RECOVERY: /* non-recoverable name server error */
159 case TRY_AGAIN: /* temporary error on authoritative server */
161 if (outlevel != O_SILENT)
162 putchar('\n'); /* terminate the progress message */
164 "nameserver failure while looking for `%s' during poll of %s.",
165 name, ctl->server.pollname);
171 * We're only here if DNS was OK but the gethostbyname() failed
172 * with a HOST_NOT_FOUND or NO_ADDRESS error.
173 * Search for a name match on MX records pointing to the server.
176 if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
180 case HOST_NOT_FOUND: /* specified host is unknown */
181 case NO_ADDRESS: /* valid, but does not have an IP address */
185 case NO_RECOVERY: /* non-recoverable name server error */
186 case TRY_AGAIN: /* temporary error on authoritative server */
189 "nameserver failure while looking for `%s' during poll of %s.",
190 name, ctl->server.pollname);
197 for (mxp = mxrecords; mxp->name; mxp++)
198 if (strcasecmp(ctl->server.truename, mxp->name) == 0)
204 /* add this name to relevant server's `also known as' list */
205 save_str(&lead_server->akalist, name, 0);
207 #endif /* HAVE_RES_SEARCH */
209 #endif /* HAVE_GETHOSTBYNAME */
211 /* checkalias.c ends here */