/*++ /* NAME /* dns_rr 3 /* SUMMARY /* resource record memory and list management /* SYNOPSIS /* #include <dns.h> /* /* DNS_RR *dns_rr_create(qname, rname, type, class, ttl, preference, /* data, data_len) /* const char *qname; /* const char *rname; /* unsigned short type; /* unsigned short class; /* unsigned int ttl; /* unsigned preference; /* const char *data; /* size_t data_len; /* /* void dns_rr_free(list) /* DNS_RR *list; /* /* DNS_RR *dns_rr_copy(record) /* DNS_RR *record; /* /* DNS_RR *dns_rr_append(list, record) /* DNS_RR *list; /* DNS_RR *record; /* /* DNS_RR *dns_rr_sort(list, compar) /* DNS_RR *list /* int (*compar)(DNS_RR *, DNS_RR *); /* /* int dns_rr_compare_pref(DNS_RR *a, DNS_RR *b) /* DNS_RR *list /* DNS_RR *list /* /* DNS_RR *dns_rr_shuffle(list) /* DNS_RR *list; /* /* DNS_RR *dns_rr_remove(list, record) /* DNS_RR *list; /* DNS_RR *record; /* DESCRIPTION /* The routines in this module maintain memory for DNS resource record /* information, and maintain lists of DNS resource records. /* /* dns_rr_create() creates and initializes one resource record. /* The \fIqname\fR field specifies the query name. /* The \fIrname\fR field specifies the reply name. /* \fIpreference\fR is used for MX records; \fIdata\fR is a null /* pointer or specifies optional resource-specific data; /* \fIdata_len\fR is the amount of resource-specific data. /* /* dns_rr_free() releases the resource used by of zero or more /* resource records. /* /* dns_rr_copy() makes a copy of a resource record. /* /* dns_rr_append() appends a resource record to a (list of) resource /* record(s). /* A null input list is explicitly allowed. /* /* dns_rr_sort() sorts a list of resource records into ascending /* order according to a user-specified criterion. The result is the /* sorted list. /* /* dns_rr_compare_pref() is a dns_rr_sort() helper to sort records /* by their MX preference. /* /* dns_rr_shuffle() randomly permutes a list of resource records. /* /* dns_rr_remove() removes the specified record from the specified list. /* The updated list is the result value. /* The record MUST be a list member. /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include <sys_defs.h> #include <string.h> #include <stdlib.h> /* Utility library. */ #include <msg.h> #include <mymalloc.h> #include <myrand.h> /* DNS library. */ #include "dns.h" /* dns_rr_create - fill in resource record structure */ DNS_RR *dns_rr_create(const char *qname, const char *rname, ushort type, ushort class, unsigned int ttl, unsigned pref, const char *data, size_t data_len) { DNS_RR *rr; rr = (DNS_RR *) mymalloc(sizeof(*rr) + data_len - 1); rr->qname = mystrdup(qname); rr->rname = mystrdup(rname); rr->type = type; rr->class = class; rr->ttl = ttl; rr->pref = pref; if (data && data_len > 0) memcpy(rr->data, data, data_len); rr->data_len = data_len; rr->next = 0; return (rr); } /* dns_rr_free - destroy resource record structure */ void dns_rr_free(DNS_RR *rr) { if (rr) { if (rr->next) dns_rr_free(rr->next); myfree(rr->qname); myfree(rr->rname); myfree((char *) rr); } } /* dns_rr_copy - copy resource record */ DNS_RR *dns_rr_copy(DNS_RR *src) { ssize_t len = sizeof(*src) + src->data_len - 1; DNS_RR *dst; /* * Combine struct assignment and data copy in one block copy operation. */ dst = (DNS_RR *) mymalloc(len); memcpy((char *) dst, (char *) src, len); dst->qname = mystrdup(src->qname); dst->rname = mystrdup(src->rname); dst->next = 0; return (dst); } /* dns_rr_append - append resource record to list */ DNS_RR *dns_rr_append(DNS_RR *list, DNS_RR *rr) { if (list == 0) { list = rr; } else { list->next = dns_rr_append(list->next, rr); } return (list); } /* dns_rr_compare_pref - compare resource records by preference */ int dns_rr_compare_pref(DNS_RR *a, DNS_RR *b) { if (a->pref != b->pref) return (a->pref - b->pref); #ifdef HAS_IPV6 if (a->type == b->type) /* 200412 */ return 0; if (a->type == T_AAAA) return (-1); if (b->type == T_AAAA) return (+1); #endif return 0; } /* dns_rr_sort_callback - glue function */ static int (*dns_rr_sort_user) (DNS_RR *, DNS_RR *); static int dns_rr_sort_callback(const void *a, const void *b) { DNS_RR *aa = *(DNS_RR **) a; DNS_RR *bb = *(DNS_RR **) b; return (dns_rr_sort_user(aa, bb)); } /* dns_rr_sort - sort resource record list */ DNS_RR *dns_rr_sort(DNS_RR *list, int (*compar) (DNS_RR *, DNS_RR *)) { int (*saved_user) (DNS_RR *, DNS_RR *); DNS_RR **rr_array; DNS_RR *rr; int len; int i; /* * Save state and initialize. */ saved_user = dns_rr_sort_user; dns_rr_sort_user = compar; /* * Build linear array with pointers to each list element. */ for (len = 0, rr = list; rr != 0; len++, rr = rr->next) /* void */ ; rr_array = (DNS_RR **) mymalloc(len * sizeof(*rr_array)); for (len = 0, rr = list; rr != 0; len++, rr = rr->next) rr_array[len] = rr; /* * Sort by user-specified criterion. */ qsort((char *) rr_array, len, sizeof(*rr_array), dns_rr_sort_callback); /* * Fix the links. */ for (i = 0; i < len - 1; i++) rr_array[i]->next = rr_array[i + 1]; rr_array[i]->next = 0; list = rr_array[0]; /* * Cleanup. */ myfree((char *) rr_array); dns_rr_sort_user = saved_user; return (list); } /* dns_rr_shuffle - shuffle resource record list */ DNS_RR *dns_rr_shuffle(DNS_RR *list) { DNS_RR **rr_array; DNS_RR *rr; int len; int i; int r; /* * Build linear array with pointers to each list element. */ for (len = 0, rr = list; rr != 0; len++, rr = rr->next) /* void */ ; rr_array = (DNS_RR **) mymalloc(len * sizeof(*rr_array)); for (len = 0, rr = list; rr != 0; len++, rr = rr->next) rr_array[len] = rr; /* * Shuffle resource records. */ for (i = 0; i < len; i++) { r = myrand() % len; rr = rr_array[i]; rr_array[i] = rr_array[r]; rr_array[r] = rr; } /* * Fix the links. */ for (i = 0; i < len - 1; i++) rr_array[i]->next = rr_array[i + 1]; rr_array[i]->next = 0; list = rr_array[0]; /* * Cleanup. */ myfree((char *) rr_array); return (list); } /* dns_rr_remove - remove record from list, return new list */ DNS_RR *dns_rr_remove(DNS_RR *list, DNS_RR *record) { if (list == 0) msg_panic("dns_rr_remove: record not found"); if (list == record) { list = record->next; record->next = 0; dns_rr_free(record); } else { list->next = dns_rr_remove(list->next, record); } return (list); }