/* * checkalias.c -- check to see if two hostnames or IP addresses are equivalent * * Copyright 1997 by Eric S. Raymond * For license terms, see the file COPYING in this directory. */ #include "config.h" #ifdef HAVE_GETHOSTBYNAME #include #include #include #include #ifdef HAVE_NET_SOCKET_H #include #else #include #endif #include #ifdef HAVE_ARPA_INET_H #include #endif #include #include "i18n.h" #include "mx.h" #include "fetchmail.h" #define MX_RETRIES 3 static int is_ip_alias(const char *name1,const char *name2) /* * Given two hostnames as arguments, returns TRUE if they * have at least one IP address in common. * No check is done on errors returned by gethostbyname, * the calling function does them. */ { typedef unsigned char address_t[sizeof (struct in_addr)]; typedef struct _address_e { struct _address_e *next; address_t address; } address_e; address_e *host_a_addr=0, *host_b_addr=0; /* assignments pacify -Wall */ address_e *dummy_addr; int i; struct hostent *hp; char **p; hp = gethostbyname(name1); dummy_addr = (address_e *)NULL; for (i=0,p = hp->h_addr_list; *p != 0; i++,p++) { struct in_addr in; (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr)); xalloca(host_a_addr, address_e *, sizeof (address_e)); memset (host_a_addr,0, sizeof (address_e)); host_a_addr->next = dummy_addr; (void) memcpy(&host_a_addr->address, *p, sizeof (in.s_addr)); dummy_addr = host_a_addr; } hp = gethostbyname(name2); dummy_addr = (address_e *)NULL; for (i=0,p = hp->h_addr_list; *p != 0; i++,p++) { struct in_addr in; (void) memcpy(&in.s_addr, *p, sizeof (in.s_addr)); xalloca(host_b_addr, address_e *, sizeof (address_e)); memset (host_b_addr,0, sizeof (address_e)); host_b_addr->next = dummy_addr; (void) memcpy(&host_b_addr->address, *p, sizeof (in.s_addr)); dummy_addr = host_b_addr; } while (host_a_addr) { while (host_b_addr) { if (!memcmp(host_b_addr->address,host_a_addr->address, sizeof (address_t))) return (TRUE); host_b_addr = host_b_addr->next; } host_a_addr = host_a_addr->next; } return (FALSE); } int is_host_alias(const char *name, struct query *ctl) /* determine whether name is a DNS alias of the mailserver for this query */ { struct hostent *he,*he_st; struct mxentry *mxp, *mxrecords; struct idlist *idl; int namelen; struct hostdata *lead_server = ctl->server.lead_server ? ctl->server.lead_server : &ctl->server; /* * The first two checks are optimizations that will catch a good * many cases. * * (1) check against the `true name' deduced from the poll label * and the via option (if present) at the beginning of the poll cycle. * Odds are good this will either be the mailserver's FQDN or a suffix of * it with the mailserver's domain's default host name omitted. * * (2) Then check the rest of the `also known as' * cache accumulated by previous DNS checks. This cache is primed * by the aka list option. * * Any of these on a mail address is definitive. Only if the * name doesn't match any is it time to call the bind library. * If this happens odds are good we're looking at an MX name. */ if (strcasecmp(lead_server->truename, name) == 0) return(TRUE); else if (str_in_list(&lead_server->akalist, name, TRUE)) return(TRUE); /* * Now check for a suffix match on the akalist. The theory here is * that if the user says `aka netaxs.com', we actually want to match * foo.netaxs.com and bar.netaxs.com. */ namelen = strlen(name); for (idl = lead_server->akalist; idl; idl = idl->next) { char *ep; /* * Test is >= here because str_in_list() should have caught the * equal-length case above. Doing it this way guarantees that * ep[-1] is a valid reference. */ if (strlen(idl->id) >= namelen)