linux/fs/nfs/dns_resolve.c

349 lines
7.4 KiB
C

/*
* linux/fs/nfs/dns_resolve.c
*
* Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
*
* Resolves DNS hostnames into valid ip addresses
*/
#include <linux/hash.h>
#include <linux/string.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/socket.h>
#include <linux/seq_file.h>
#include <linux/inet.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/cache.h>
#include <linux/sunrpc/svcauth.h>
#include "dns_resolve.h"
#include "cache_lib.h"
#define NFS_DNS_HASHBITS 4
#define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
static struct cache_head *nfs_dns_table[NFS_DNS_HASHTBL_SIZE];
struct nfs_dns_ent {
struct cache_head h;
char *hostname;
size_t namelen;
struct sockaddr_storage addr;
size_t addrlen;
};
static void nfs_dns_ent_update(struct cache_head *cnew,
struct cache_head *ckey)
{
struct nfs_dns_ent *new;
struct nfs_dns_ent *key;
new = container_of(cnew, struct nfs_dns_ent, h);
key = container_of(ckey, struct nfs_dns_ent, h);
memcpy(&new->addr, &key->addr, key->addrlen);
new->addrlen = key->addrlen;
}
static void nfs_dns_ent_init(struct cache_head *cnew,
struct cache_head *ckey)
{
struct nfs_dns_ent *new;
struct nfs_dns_ent *key;
new = container_of(cnew, struct nfs_dns_ent, h);
key = container_of(ckey, struct nfs_dns_ent, h);
kfree(new->hostname);
new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
if (new->hostname) {
new->namelen = key->namelen;
nfs_dns_ent_update(cnew, ckey);
} else {
new->namelen = 0;
new->addrlen = 0;
}
}
static void nfs_dns_ent_put(struct kref *ref)
{
struct nfs_dns_ent *item;
item = container_of(ref, struct nfs_dns_ent, h.ref);
kfree(item->hostname);
kfree(item);
}
static struct cache_head *nfs_dns_ent_alloc(void)
{
struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
if (item != NULL) {
item->hostname = NULL;
item->namelen = 0;
item->addrlen = 0;
return &item->h;
}
return NULL;
};
static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
{
return hash_str(key->hostname, NFS_DNS_HASHBITS);
}
static void nfs_dns_request(struct cache_detail *cd,
struct cache_head *ch,
char **bpp, int *blen)
{
struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
qword_add(bpp, blen, key->hostname);
(*bpp)[-1] = '\n';
}
static int nfs_dns_upcall(struct cache_detail *cd,
struct cache_head *ch)
{
struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
int ret;
ret = nfs_cache_upcall(cd, key->hostname);
if (ret)
ret = sunrpc_cache_pipe_upcall(cd, ch, nfs_dns_request);
return ret;
}
static int nfs_dns_match(struct cache_head *ca,
struct cache_head *cb)
{
struct nfs_dns_ent *a;
struct nfs_dns_ent *b;
a = container_of(ca, struct nfs_dns_ent, h);
b = container_of(cb, struct nfs_dns_ent, h);
if (a->namelen == 0 || a->namelen != b->namelen)
return 0;
return memcmp(a->hostname, b->hostname, a->namelen) == 0;
}
static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
struct cache_head *h)
{
struct nfs_dns_ent *item;
long ttl;
if (h == NULL) {
seq_puts(m, "# ip address hostname ttl\n");
return 0;
}
item = container_of(h, struct nfs_dns_ent, h);
ttl = (long)item->h.expiry_time - (long)get_seconds();
if (ttl < 0)
ttl = 0;
if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
seq_printf(m, "%15s ", buf);
} else
seq_puts(m, "<none> ");
seq_printf(m, "%15s %ld\n", item->hostname, ttl);
return 0;
}
static struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
struct nfs_dns_ent *key)
{
struct cache_head *ch;
ch = sunrpc_cache_lookup(cd,
&key->h,
nfs_dns_hash(key));
if (!ch)
return NULL;
return container_of(ch, struct nfs_dns_ent, h);
}
static struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
struct nfs_dns_ent *new,
struct nfs_dns_ent *key)
{
struct cache_head *ch;
ch = sunrpc_cache_update(cd,
&new->h, &key->h,
nfs_dns_hash(key));
if (!ch)
return NULL;
return container_of(ch, struct nfs_dns_ent, h);
}
static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
{
char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
struct nfs_dns_ent key, *item;
unsigned long ttl;
ssize_t len;
int ret = -EINVAL;
if (buf[buflen-1] != '\n')
goto out;
buf[buflen-1] = '\0';
len = qword_get(&buf, buf1, sizeof(buf1));
if (len <= 0)
goto out;
key.addrlen = rpc_pton(buf1, len,
(struct sockaddr *)&key.addr,
sizeof(key.addr));
len = qword_get(&buf, buf1, sizeof(buf1));
if (len <= 0)
goto out;
key.hostname = buf1;
key.namelen = len;
memset(&key.h, 0, sizeof(key.h));
ttl = get_expiry(&buf);
if (ttl == 0)
goto out;
key.h.expiry_time = ttl + get_seconds();
ret = -ENOMEM;
item = nfs_dns_lookup(cd, &key);
if (item == NULL)
goto out;
if (key.addrlen == 0)
set_bit(CACHE_NEGATIVE, &key.h.flags);
item = nfs_dns_update(cd, &key, item);
if (item == NULL)
goto out;
ret = 0;
cache_put(&item->h, cd);
out:
return ret;
}
static struct cache_detail nfs_dns_resolve = {
.owner = THIS_MODULE,
.hash_size = NFS_DNS_HASHTBL_SIZE,
.hash_table = nfs_dns_table,
.name = "dns_resolve",
.cache_put = nfs_dns_ent_put,
.cache_upcall = nfs_dns_upcall,
.cache_parse = nfs_dns_parse,
.cache_show = nfs_dns_show,
.match = nfs_dns_match,
.init = nfs_dns_ent_init,
.update = nfs_dns_ent_update,
.alloc = nfs_dns_ent_alloc,
};
static int do_cache_lookup(struct cache_detail *cd,
struct nfs_dns_ent *key,
struct nfs_dns_ent **item,
struct nfs_cache_defer_req *dreq)
{
int ret = -ENOMEM;
*item = nfs_dns_lookup(cd, key);
if (*item) {
ret = cache_check(cd, &(*item)->h, &dreq->req);
if (ret)
*item = NULL;
}
return ret;
}
static int do_cache_lookup_nowait(struct cache_detail *cd,
struct nfs_dns_ent *key,
struct nfs_dns_ent **item)
{
int ret = -ENOMEM;
*item = nfs_dns_lookup(cd, key);
if (!*item)
goto out_err;
ret = -ETIMEDOUT;
if (!test_bit(CACHE_VALID, &(*item)->h.flags)
|| (*item)->h.expiry_time < get_seconds()
|| cd->flush_time > (*item)->h.last_refresh)
goto out_put;
ret = -ENOENT;
if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
goto out_put;
return 0;
out_put:
cache_put(&(*item)->h, cd);
out_err:
*item = NULL;
return ret;
}
static int do_cache_lookup_wait(struct cache_detail *cd,
struct nfs_dns_ent *key,
struct nfs_dns_ent **item)
{
struct nfs_cache_defer_req *dreq;
int ret = -ENOMEM;
dreq = nfs_cache_defer_req_alloc();
if (!dreq)
goto out;
ret = do_cache_lookup(cd, key, item, dreq);
if (ret == -EAGAIN) {
ret = nfs_cache_wait_for_upcall(dreq);
if (!ret)
ret = do_cache_lookup_nowait(cd, key, item);
}
nfs_cache_defer_req_put(dreq);
out:
return ret;
}
ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
struct sockaddr *sa, size_t salen)
{
struct nfs_dns_ent key = {
.hostname = name,
.namelen = namelen,
};
struct nfs_dns_ent *item = NULL;
ssize_t ret;
ret = do_cache_lookup_wait(&nfs_dns_resolve, &key, &item);
if (ret == 0) {
if (salen >= item->addrlen) {
memcpy(sa, &item->addr, item->addrlen);
ret = item->addrlen;
} else
ret = -EOVERFLOW;
cache_put(&item->h, &nfs_dns_resolve);
} else if (ret == -ENOENT)
ret = -ESRCH;
return ret;
}
int nfs_dns_resolver_init(void)
{
return nfs_cache_register(&nfs_dns_resolve);
}
void nfs_dns_resolver_destroy(void)
{
nfs_cache_unregister(&nfs_dns_resolve);
}