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>
19 #include "fetchmail.h"
23 static int is_ip_alias(const char *name1,const char *name2)
25 * Given two hostnames as arguments, returns TRUE if they
26 * have at least one IP address in common.
27 * No check is done on errors returned by gethostbyname,
28 * the calling function does them.
31 typedef unsigned char address_t[sizeof (struct in_addr)];
32 typedef struct _address_e
34 struct _address_e *next;
38 address_e *host_a_addr=0, *host_b_addr=0; /* assignments pacify -Wall */
39 address_e *dummy_addr;
45 hp = gethostbyname(name1);
47 dummy_addr = (address_e *)NULL;
49 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
52 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
53 xalloca(host_a_addr, address_e *, sizeof (address_e));
54 memset (host_a_addr,0, sizeof (address_e));
55 host_a_addr->next = dummy_addr;
56 (void) memcpy(&host_a_addr->address, *p, sizeof (in.s_addr));
57 dummy_addr = host_a_addr;
60 hp = gethostbyname(name2);
62 dummy_addr = (address_e *)NULL;
63 for (i=0,p = hp->h_addr_list; *p != 0; i++,p++)
66 (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr));
67 xalloca(host_b_addr, address_e *, sizeof (address_e));
68 memset (host_b_addr,0, sizeof (address_e));
69 host_b_addr->next = dummy_addr;
70 (void) memcpy(&host_b_addr->address, *p, sizeof (in.s_addr));
71 dummy_addr = host_b_addr;
78 if (!memcmp(host_b_addr->address,host_a_addr->address, sizeof (address_t)))
81 host_b_addr = host_b_addr->next;
83 host_a_addr = host_a_addr->next;
88 int is_host_alias(const char *name, struct query *ctl)
89 /* determine whether name is a DNS alias of the mailserver for this query */
91 struct hostent *he,*he_st;
92 struct mxentry *mxp, *mxrecords;
96 struct hostdata *lead_server =
97 ctl->server.lead_server ? ctl->server.lead_server : &ctl->server;
100 * The first two checks are optimizations that will catch a good
103 * (1) check against the `true name' deduced from the poll label
104 * and the via option (if present) at the beginning of the poll cycle.
105 * Odds are good this will either be the mailserver's FQDN or a suffix of
106 * it with the mailserver's domain's default host name omitted.
108 * (2) Then check the rest of the `also known as'
109 * cache accumulated by previous DNS checks. This cache is primed
110 * by the aka list option.
112 * Any of these on a mail address is definitive. Only if the
113 * name doesn't match any is it time to call the bind library.
114 * If this happens odds are good we're looking at an MX name.
116 if (strcasecmp(lead_server->truename, name) == 0)
118 else if (str_in_list(&lead_server->akalist, name, TRUE))
120 else if (!ctl->server.dns)
124 * Now check for a suffix match on the akalist. The theory here is
125 * that if the user says `aka netaxs.com', we actually want to match
126 * foo.netaxs.com and bar.netaxs.com.
128 namelen = strlen(name);
129 for (idl = lead_server->akalist; idl; idl = idl->next)
134 * Test is <= here because str_in_list() should have caught the
135 * equal-length case above. Doing it this way guarantees that
136 * ep[-1] is a valid reference.
138 if (strlen(idl->id) <= namelen)
140 ep = idl->id + (strlen(idl->id) - namelen);
141 /* a suffix led by . must match */
142 if (ep[-1] == '.' && !strcmp(ep, name))
146 #ifndef HAVE_RES_SEARCH
150 * The only code that calls the BIND library is here and in the
151 * start-of-run probe with gethostbyname(3) under ETRN/Kerberos.
153 * We know DNS service was up at the beginning of the run.
154 * If it's down, our nameserver has crashed. We don't want to try
155 * delivering the current message or anything else from the
156 * current server until it's back up.
158 if ((he = gethostbyname(name)) != (struct hostent *)NULL)
160 if (strcasecmp(ctl->server.truename, he->h_name) == 0)
162 else if (((he_st = gethostbyname(ctl->server.truename)) != (struct hostent *)NULL) && ctl->server.checkalias)
164 if (outlevel >= O_DEBUG)
165 report(stdout, _("Checking if %s is really the same node as %s\n"),ctl->server.truename,name);
166 if (is_ip_alias(ctl->server.truename,name) == TRUE)
168 if (outlevel >= O_DEBUG)
169 report(stdout, _("Yes, their IP addresses match\n"));
172 if (outlevel >= O_DEBUG)
173 report(stdout, _("No, their IP addresses don't match\n"));
182 case HOST_NOT_FOUND: /* specified host is unknown */
183 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 */
189 if (outlevel != O_SILENT)
190 report_complete(stdout, "\n"); /* terminate the progress message */
192 _("nameserver failure while looking for `%s' during poll of %s.\n"),
193 name, ctl->server.pollname);
199 * We're only here if DNS was OK but the gethostbyname() failed
200 * with a HOST_NOT_FOUND or NO_ADDRESS error.
201 * Search for a name match on MX records pointing to the server.
204 if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL)
208 case HOST_NOT_FOUND: /* specified host is unknown */
209 case NO_ADDRESS: /* valid, but does not have an IP address */
213 case NO_RECOVERY: /* non-recoverable name server error */
214 case TRY_AGAIN: /* temporary error on authoritative server */
217 _("nameserver failure while looking for `%s' during poll of %s.\n"),
218 name, ctl->server.pollname);
225 for (mxp = mxrecords; mxp->name; mxp++)
226 if (strcasecmp(ctl->server.truename, mxp->name) == 0)
232 /* add this name to relevant server's `also known as' list */
233 save_str(&lead_server->akalist, name, 0);
235 #endif /* HAVE_RES_SEARCH */
237 #endif /* HAVE_GETHOSTBYNAME */
239 /* checkalias.c ends here */