NFS: Add a dns resolver for use with NFSv4 referrals and migration
The NFSv4 and NFSv4.1 protocols both allow for the redirection of a client from one server to another in order to support filesystem migration and replication. For full protocol support, we need to add the ability to convert a DNS host name into an IP address that we can feed to the RPC client. We'll reuse the sunrpc cache, now that it has been converted to work with rpc_pipefs. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
335
fs/nfs/dns_resolve.c
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335
fs/nfs/dns_resolve.c
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/*
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* linux/fs/nfs/dns_resolve.c
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*
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* Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
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*
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* Resolves DNS hostnames into valid ip addresses
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*/
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#include <linux/hash.h>
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#include <linux/string.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/socket.h>
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#include <linux/seq_file.h>
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#include <linux/inet.h>
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#include <linux/sunrpc/clnt.h>
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#include <linux/sunrpc/cache.h>
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#include <linux/sunrpc/svcauth.h>
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#include "dns_resolve.h"
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#include "cache_lib.h"
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#define NFS_DNS_HASHBITS 4
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#define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
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static struct cache_head *nfs_dns_table[NFS_DNS_HASHTBL_SIZE];
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struct nfs_dns_ent {
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struct cache_head h;
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char *hostname;
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size_t namelen;
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struct sockaddr_storage addr;
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size_t addrlen;
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};
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static void nfs_dns_ent_init(struct cache_head *cnew,
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struct cache_head *ckey)
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{
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struct nfs_dns_ent *new;
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struct nfs_dns_ent *key;
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new = container_of(cnew, struct nfs_dns_ent, h);
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key = container_of(ckey, struct nfs_dns_ent, h);
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kfree(new->hostname);
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new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
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if (new->hostname) {
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new->namelen = key->namelen;
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memcpy(&new->addr, &key->addr, key->addrlen);
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new->addrlen = key->addrlen;
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} else {
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new->namelen = 0;
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new->addrlen = 0;
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}
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}
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static void nfs_dns_ent_put(struct kref *ref)
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{
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struct nfs_dns_ent *item;
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item = container_of(ref, struct nfs_dns_ent, h.ref);
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kfree(item->hostname);
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kfree(item);
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}
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static struct cache_head *nfs_dns_ent_alloc(void)
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{
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struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
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if (item != NULL) {
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item->hostname = NULL;
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item->namelen = 0;
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item->addrlen = 0;
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return &item->h;
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}
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return NULL;
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};
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static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
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{
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return hash_str(key->hostname, NFS_DNS_HASHBITS);
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}
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static void nfs_dns_request(struct cache_detail *cd,
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struct cache_head *ch,
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char **bpp, int *blen)
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{
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struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
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qword_add(bpp, blen, key->hostname);
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(*bpp)[-1] = '\n';
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}
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static int nfs_dns_upcall(struct cache_detail *cd,
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struct cache_head *ch)
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{
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struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
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int ret;
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ret = nfs_cache_upcall(cd, key->hostname);
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if (ret)
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ret = sunrpc_cache_pipe_upcall(cd, ch, nfs_dns_request);
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return ret;
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}
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static int nfs_dns_match(struct cache_head *ca,
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struct cache_head *cb)
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{
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struct nfs_dns_ent *a;
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struct nfs_dns_ent *b;
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a = container_of(ca, struct nfs_dns_ent, h);
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b = container_of(cb, struct nfs_dns_ent, h);
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if (a->namelen == 0 || a->namelen != b->namelen)
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return 0;
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return memcmp(a->hostname, b->hostname, a->namelen) == 0;
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}
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static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
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struct cache_head *h)
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{
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struct nfs_dns_ent *item;
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long ttl;
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if (h == NULL) {
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seq_puts(m, "# ip address hostname ttl\n");
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return 0;
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}
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item = container_of(h, struct nfs_dns_ent, h);
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ttl = (long)item->h.expiry_time - (long)get_seconds();
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if (ttl < 0)
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ttl = 0;
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if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
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char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
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rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
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seq_printf(m, "%15s ", buf);
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} else
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seq_puts(m, "<none> ");
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seq_printf(m, "%15s %ld\n", item->hostname, ttl);
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return 0;
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}
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struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
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struct nfs_dns_ent *key)
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{
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struct cache_head *ch;
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ch = sunrpc_cache_lookup(cd,
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&key->h,
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nfs_dns_hash(key));
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if (!ch)
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return NULL;
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return container_of(ch, struct nfs_dns_ent, h);
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}
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struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
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struct nfs_dns_ent *new,
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struct nfs_dns_ent *key)
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{
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struct cache_head *ch;
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ch = sunrpc_cache_update(cd,
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&new->h, &key->h,
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nfs_dns_hash(key));
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if (!ch)
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return NULL;
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return container_of(ch, struct nfs_dns_ent, h);
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}
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static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
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{
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char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
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struct nfs_dns_ent key, *item;
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unsigned long ttl;
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ssize_t len;
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int ret = -EINVAL;
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if (buf[buflen-1] != '\n')
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goto out;
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buf[buflen-1] = '\0';
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len = qword_get(&buf, buf1, sizeof(buf1));
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if (len <= 0)
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goto out;
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key.addrlen = rpc_pton(buf1, len,
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(struct sockaddr *)&key.addr,
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sizeof(key.addr));
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len = qword_get(&buf, buf1, sizeof(buf1));
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if (len <= 0)
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goto out;
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key.hostname = buf1;
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key.namelen = len;
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memset(&key.h, 0, sizeof(key.h));
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ttl = get_expiry(&buf);
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if (ttl == 0)
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goto out;
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key.h.expiry_time = ttl + get_seconds();
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ret = -ENOMEM;
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item = nfs_dns_lookup(cd, &key);
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if (item == NULL)
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goto out;
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if (key.addrlen == 0)
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set_bit(CACHE_NEGATIVE, &key.h.flags);
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item = nfs_dns_update(cd, &key, item);
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if (item == NULL)
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goto out;
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ret = 0;
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cache_put(&item->h, cd);
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out:
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return ret;
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}
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static struct cache_detail nfs_dns_resolve = {
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.owner = THIS_MODULE,
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.hash_size = NFS_DNS_HASHTBL_SIZE,
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.hash_table = nfs_dns_table,
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.name = "dns_resolve",
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.cache_put = nfs_dns_ent_put,
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.cache_upcall = nfs_dns_upcall,
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.cache_parse = nfs_dns_parse,
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.cache_show = nfs_dns_show,
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.match = nfs_dns_match,
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.init = nfs_dns_ent_init,
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.update = nfs_dns_ent_init,
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.alloc = nfs_dns_ent_alloc,
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};
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static int do_cache_lookup(struct cache_detail *cd,
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struct nfs_dns_ent *key,
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struct nfs_dns_ent **item,
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struct nfs_cache_defer_req *dreq)
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{
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int ret = -ENOMEM;
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*item = nfs_dns_lookup(cd, key);
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if (*item) {
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ret = cache_check(cd, &(*item)->h, &dreq->req);
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if (ret)
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*item = NULL;
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}
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return ret;
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}
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static int do_cache_lookup_nowait(struct cache_detail *cd,
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struct nfs_dns_ent *key,
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struct nfs_dns_ent **item)
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{
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int ret = -ENOMEM;
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*item = nfs_dns_lookup(cd, key);
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if (!*item)
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goto out_err;
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ret = -ETIMEDOUT;
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if (!test_bit(CACHE_VALID, &(*item)->h.flags)
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|| (*item)->h.expiry_time < get_seconds()
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|| cd->flush_time > (*item)->h.last_refresh)
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goto out_put;
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ret = -ENOENT;
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if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
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goto out_put;
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return 0;
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out_put:
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cache_put(&(*item)->h, cd);
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out_err:
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*item = NULL;
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return ret;
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}
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static int do_cache_lookup_wait(struct cache_detail *cd,
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struct nfs_dns_ent *key,
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struct nfs_dns_ent **item)
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{
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struct nfs_cache_defer_req *dreq;
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int ret = -ENOMEM;
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dreq = nfs_cache_defer_req_alloc();
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if (!dreq)
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goto out;
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ret = do_cache_lookup(cd, key, item, dreq);
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if (ret == -EAGAIN) {
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ret = nfs_cache_wait_for_upcall(dreq);
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if (!ret)
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ret = do_cache_lookup_nowait(cd, key, item);
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}
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nfs_cache_defer_req_put(dreq);
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out:
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return ret;
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}
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ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
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struct sockaddr *sa, size_t salen)
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{
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struct nfs_dns_ent key = {
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.hostname = name,
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.namelen = namelen,
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};
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struct nfs_dns_ent *item = NULL;
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ssize_t ret;
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ret = do_cache_lookup_wait(&nfs_dns_resolve, &key, &item);
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if (ret == 0) {
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if (salen >= item->addrlen) {
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memcpy(sa, &item->addr, item->addrlen);
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ret = item->addrlen;
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} else
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ret = -EOVERFLOW;
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cache_put(&item->h, &nfs_dns_resolve);
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} else if (ret == -ENOENT)
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ret = -ESRCH;
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return ret;
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}
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int nfs_dns_resolver_init(void)
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{
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return nfs_cache_register(&nfs_dns_resolve);
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}
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void nfs_dns_resolver_destroy(void)
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{
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nfs_cache_unregister(&nfs_dns_resolve);
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}
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