diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/dnscache.c | 92 |
1 files changed, 78 insertions, 14 deletions
diff --git a/src/dnscache.c b/src/dnscache.c index 8ec3b69..6ff89f1 100644 --- a/src/dnscache.c +++ b/src/dnscache.c @@ -1,4 +1,4 @@ -/* $Id: dnscache.c,v 1.9 2001-05-27 02:24:00 rjkaes Exp $ +/* $Id: dnscache.c,v 1.10 2001-08-29 03:57:51 rjkaes Exp $ * * This is a caching DNS system. When a host name is needed we look it up here * and see if there is already an answer for it. The domains are placed in a @@ -34,6 +34,14 @@ #include "ternary.h" #include "utils.h" +/* + * The mutex is used for locking around accesses to the ternary tree. + */ +static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; + +#define LOCK() pthread_mutex_lock(&mutex); +#define UNLOCK() pthread_mutex_unlock(&mutex); + #define DNSEXPIRE (5 * 60) struct dnscache_s { @@ -41,49 +49,94 @@ struct dnscache_s { time_t expire; }; -static TERNARY dns_tree; +static TERNARY dns_tree = -1; -TERNARY new_dnscache(void) +/* + * Insert the data into the DNS tree. + */ +static int insert_data(char *domain, struct dnscache_s *newptr) { - dns_tree = ternary_new(); + int ret; + + LOCK(); + ret = ternary_insert(dns_tree, domain, newptr); + UNLOCK(); - return dns_tree; + return ret; } static int dns_lookup(struct in_addr *addr, char *domain) { + int ret; struct dnscache_s *ptr; assert(addr != NULL); assert(domain != NULL); - if (TE_ISERROR(ternary_search(dns_tree, domain, (void *)&ptr))) - return -1; + LOCK(); + ret = ternary_search(dns_tree, domain, (void *)&ptr); - if (difftime(time(NULL), ptr->expire) > (double)DNSEXPIRE) { + if (TE_ISERROR(ret) + || difftime(time(NULL), ptr->expire) > DNSEXPIRE) { + UNLOCK(); return -1; } - *addr = ptr->ipaddr; + memcpy(addr, &ptr->ipaddr, sizeof(struct in_addr)); + UNLOCK(); + return 0; } static int dns_insert(struct in_addr *addr, char *domain) { struct dnscache_s *newptr; + int ret; assert(addr != NULL); assert(domain != NULL); + DEBUG2("Inserting [%s] into DNS cache", domain); + if (!(newptr = malloc(sizeof(struct dnscache_s)))) { return -1; } - newptr->ipaddr = *addr; + memcpy(&newptr->ipaddr, addr, sizeof(struct in_addr)); newptr->expire = time(NULL); - if (TE_ISERROR(ternary_insert(dns_tree, domain, newptr))) - safefree(newptr); + ret = insert_data(domain, newptr); + + if (TE_ISERROR(ret)) { + if (ret == TE_EXISTS) { + /* + * The value already exists. First search for the + * value and then delete the data before inserting + * the new value. + */ + struct dnscache_s *existing; + + DEBUG2("[%s] already exists in DNS cache", domain); + + LOCK(); + ret = ternary_search(dns_tree, domain, (void *)&existing); + UNLOCK(); + + if (TE_ISERROR(ret)) + goto INSERT_ERROR; + + safefree(existing); + + ret = insert_data(domain, newptr); + + if (TE_ISERROR(ret)) + goto INSERT_ERROR; + } else { + INSERT_ERROR: + safefree(newptr); + return -1; + } + } return 0; } @@ -95,7 +148,13 @@ int dnscache(struct in_addr *addr, char *domain) assert(addr != NULL); assert(domain != NULL); - if (inet_aton(domain, (struct in_addr *) addr) != 0) + /* If the DNS tree doesn't exist, build a new one */ + LOCK(); + if (dns_tree < 0) + dns_tree = ternary_new(); + UNLOCK(); + + if (inet_aton(domain, (struct in_addr *)addr) != 0) return 0; /* Well, we're not dotted-decimal so we need to look it up */ @@ -103,10 +162,15 @@ int dnscache(struct in_addr *addr, char *domain) return 0; /* Okay, so not in the list... need to actually look it up. */ - if (!(resolv = gethostbyname(domain))) + LOCK(); + if (!(resolv = gethostbyname(domain))) { + UNLOCK(); return -1; + } memcpy(addr, resolv->h_addr_list[0], (size_t)resolv->h_length); + UNLOCK(); + dns_insert(addr, domain); return 0; |