/*
   * linux/fs/nfs/dns_resolve.c
   *
   * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
   *
   * Resolves DNS hostnames into valid ip addresses
   */

  #ifdef CONFIG_NFS_USE_KERNEL_DNS
  
  #include <linux/sunrpc/clnt.h>
  #include <linux/dns_resolver.h>
  
  ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
  		struct sockaddr *sa, size_t salen)
  {
  	ssize_t ret;
  	char *ip_addr = NULL;
  	int ip_len;
  
  	ip_len = dns_query(NULL, name, namelen, NULL, &ip_addr, NULL);
  	if (ip_len > 0)
  		ret = rpc_pton(ip_addr, ip_len, sa, salen);
  	else
  		ret = -ESRCH;
  	kfree(ip_addr);
  	return ret;
  }
  
  #else

  #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] = '
  ';
  }
  
  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
  ");
  		return 0;
  	}
  	item = container_of(h, struct nfs_dns_ent, h);

  	ttl = item->h.expiry_time - seconds_since_boot();

  	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
  ", 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] != '
  ')
  		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 + seconds_since_boot();

  
  	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 < seconds_since_boot()

  			|| 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);
  }

  #endif