dns_resolve.c

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/*
 * linux/fs/nfs/dns_resolve.c
 *
 * Copyright (c) 2009 Trond Myklebust <[email protected]>
 *
 * Resolves DNS hostnames into valid ip addresses
 */

#ifdef CONFIG_NFS_USE_KERNEL_DNS

#include <linux/module.h>
#include <linux/sunrpc/clnt.h>
#include <linux/dns_resolver.h>
#include "dns_resolve.h"

ssize_t nfs_dns_resolve_name(struct net *net, 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(net, ip_addr, ip_len, sa, salen);
    else
        ret = -ESRCH;
    kfree(ip_addr);
    return ret;
}
EXPORT_SYMBOL_GPL(nfs_dns_resolve_name);

#else

#include <linux/module.h>
#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 <linux/sunrpc/rpc_pipe_fs.h>

#include "dns_resolve.h"
#include "cache_lib.h"
#include "netns.h"

#define NFS_DNS_HASHBITS 4
#define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)

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 = 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\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 int 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(cd->net, 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));

    if (get_uint(&buf, &ttl) < 0)
        goto out;
    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 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(struct net *net, 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;
    struct nfs_net *nn = net_generic(net, nfs_net_id);

    ret = do_cache_lookup_wait(nn->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, nn->nfs_dns_resolve);
    } else if (ret == -ENOENT)
        ret = -ESRCH;
    return ret;
}
EXPORT_SYMBOL_GPL(nfs_dns_resolve_name);

int nfs_dns_resolver_cache_init(struct net *net)
{
    int err = -ENOMEM;
    struct nfs_net *nn = net_generic(net, nfs_net_id);
    struct cache_detail *cd;
    struct cache_head **tbl;

    cd = kzalloc(sizeof(struct cache_detail), GFP_KERNEL);
    if (cd == NULL)
        goto err_cd;

    tbl = kzalloc(NFS_DNS_HASHTBL_SIZE * sizeof(struct cache_head *),
            GFP_KERNEL);
    if (tbl == NULL)
        goto err_tbl;

    cd->owner = THIS_MODULE,
    cd->hash_size = NFS_DNS_HASHTBL_SIZE,
    cd->hash_table = tbl,
    cd->name = "dns_resolve",
    cd->cache_put = nfs_dns_ent_put,
    cd->cache_upcall = nfs_dns_upcall,
    cd->cache_parse = nfs_dns_parse,
    cd->cache_show = nfs_dns_show,
    cd->match = nfs_dns_match,
    cd->init = nfs_dns_ent_init,
    cd->update = nfs_dns_ent_update,
    cd->alloc = nfs_dns_ent_alloc,

    nfs_cache_init(cd);
    err = nfs_cache_register_net(net, cd);
    if (err)
        goto err_reg;
    nn->nfs_dns_resolve = cd;
    return 0;

err_reg:
    nfs_cache_destroy(cd);
    kfree(cd->hash_table);
err_tbl:
    kfree(cd);
err_cd:
    return err;
}

void nfs_dns_resolver_cache_destroy(struct net *net)
{
    struct nfs_net *nn = net_generic(net, nfs_net_id);
    struct cache_detail *cd = nn->nfs_dns_resolve;

    nfs_cache_unregister_net(net, cd);
    nfs_cache_destroy(cd);
    kfree(cd->hash_table);
    kfree(cd);
}

static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
               void *ptr)
{
    struct super_block *sb = ptr;
    struct net *net = sb->s_fs_info;
    struct nfs_net *nn = net_generic(net, nfs_net_id);
    struct cache_detail *cd = nn->nfs_dns_resolve;
    int ret = 0;

    if (cd == NULL)
        return 0;

    if (!try_module_get(THIS_MODULE))
        return 0;

    switch (event) {
    case RPC_PIPEFS_MOUNT:
        ret = nfs_cache_register_sb(sb, cd);
        break;
    case RPC_PIPEFS_UMOUNT:
        nfs_cache_unregister_sb(sb, cd);
        break;
    default:
        ret = -ENOTSUPP;
        break;
    }
    module_put(THIS_MODULE);
    return ret;
}

static struct notifier_block nfs_dns_resolver_block = {
    .notifier_call  = rpc_pipefs_event,
};

int nfs_dns_resolver_init(void)
{
    return rpc_pipefs_notifier_register(&nfs_dns_resolver_block);
}

void nfs_dns_resolver_destroy(void)
{
    rpc_pipefs_notifier_unregister(&nfs_dns_resolver_block);
}
#endif