anycast.c

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/*
 *  Anycast support for IPv6
 *  Linux INET6 implementation
 *
 *  Authors:
 *  David L Stevens ([email protected])
 *
 *  based heavily on net/ipv6/mcast.c
 *
 *  This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/random.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/route.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/snmp.h>

#include <net/ipv6.h>
#include <net/protocol.h>
#include <net/if_inet6.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
#include <net/ip6_route.h>

#include <net/checksum.h>

static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr);

/* Big ac list lock for all the sockets */
static DEFINE_RWLOCK(ipv6_sk_ac_lock);


/*
 *  socket join an anycast group
 */

int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
{
    struct ipv6_pinfo *np = inet6_sk(sk);
    struct net_device *dev = NULL;
    struct inet6_dev *idev;
    struct ipv6_ac_socklist *pac;
    struct net *net = sock_net(sk);
    int ishost = !net->ipv6.devconf_all->forwarding;
    int err = 0;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;
    if (ipv6_addr_is_multicast(addr))
        return -EINVAL;
    if (ipv6_chk_addr(net, addr, NULL, 0))
        return -EINVAL;

    pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
    if (pac == NULL)
        return -ENOMEM;
    pac->acl_next = NULL;
    pac->acl_addr = *addr;

    rcu_read_lock();
    if (ifindex == 0) {
        struct rt6_info *rt;

        rt = rt6_lookup(net, addr, NULL, 0, 0);
        if (rt) {
            dev = rt->dst.dev;
            dst_release(&rt->dst);
        } else if (ishost) {
            err = -EADDRNOTAVAIL;
            goto error;
        } else {
            /* router, no matching interface: just pick one */
            dev = dev_get_by_flags_rcu(net, IFF_UP,
                           IFF_UP | IFF_LOOPBACK);
        }
    } else
        dev = dev_get_by_index_rcu(net, ifindex);

    if (dev == NULL) {
        err = -ENODEV;
        goto error;
    }

    idev = __in6_dev_get(dev);
    if (!idev) {
        if (ifindex)
            err = -ENODEV;
        else
            err = -EADDRNOTAVAIL;
        goto error;
    }
    /* reset ishost, now that we have a specific device */
    ishost = !idev->cnf.forwarding;

    pac->acl_ifindex = dev->ifindex;

    /* XXX
     * For hosts, allow link-local or matching prefix anycasts.
     * This obviates the need for propagating anycast routes while
     * still allowing some non-router anycast participation.
     */
    if (!ipv6_chk_prefix(addr, dev)) {
        if (ishost)
            err = -EADDRNOTAVAIL;
        if (err)
            goto error;
    }

    err = ipv6_dev_ac_inc(dev, addr);
    if (!err) {
        write_lock_bh(&ipv6_sk_ac_lock);
        pac->acl_next = np->ipv6_ac_list;
        np->ipv6_ac_list = pac;
        write_unlock_bh(&ipv6_sk_ac_lock);
        pac = NULL;
    }

error:
    rcu_read_unlock();
    if (pac)
        sock_kfree_s(sk, pac, sizeof(*pac));
    return err;
}

/*
 *  socket leave an anycast group
 */
int ipv6_sock_ac_drop(struct sock *sk, int ifindex, const struct in6_addr *addr)
{
    struct ipv6_pinfo *np = inet6_sk(sk);
    struct net_device *dev;
    struct ipv6_ac_socklist *pac, *prev_pac;
    struct net *net = sock_net(sk);

    write_lock_bh(&ipv6_sk_ac_lock);
    prev_pac = NULL;
    for (pac = np->ipv6_ac_list; pac; pac = pac->acl_next) {
        if ((ifindex == 0 || pac->acl_ifindex == ifindex) &&
             ipv6_addr_equal(&pac->acl_addr, addr))
            break;
        prev_pac = pac;
    }
    if (!pac) {
        write_unlock_bh(&ipv6_sk_ac_lock);
        return -ENOENT;
    }
    if (prev_pac)
        prev_pac->acl_next = pac->acl_next;
    else
        np->ipv6_ac_list = pac->acl_next;

    write_unlock_bh(&ipv6_sk_ac_lock);

    rcu_read_lock();
    dev = dev_get_by_index_rcu(net, pac->acl_ifindex);
    if (dev)
        ipv6_dev_ac_dec(dev, &pac->acl_addr);
    rcu_read_unlock();

    sock_kfree_s(sk, pac, sizeof(*pac));
    return 0;
}

void ipv6_sock_ac_close(struct sock *sk)
{
    struct ipv6_pinfo *np = inet6_sk(sk);
    struct net_device *dev = NULL;
    struct ipv6_ac_socklist *pac;
    struct net *net = sock_net(sk);
    int prev_index;

    write_lock_bh(&ipv6_sk_ac_lock);
    pac = np->ipv6_ac_list;
    np->ipv6_ac_list = NULL;
    write_unlock_bh(&ipv6_sk_ac_lock);

    prev_index = 0;
    rcu_read_lock();
    while (pac) {
        struct ipv6_ac_socklist *next = pac->acl_next;

        if (pac->acl_ifindex != prev_index) {
            dev = dev_get_by_index_rcu(net, pac->acl_ifindex);
            prev_index = pac->acl_ifindex;
        }
        if (dev)
            ipv6_dev_ac_dec(dev, &pac->acl_addr);
        sock_kfree_s(sk, pac, sizeof(*pac));
        pac = next;
    }
    rcu_read_unlock();
}

static void aca_put(struct ifacaddr6 *ac)
{
    if (atomic_dec_and_test(&ac->aca_refcnt)) {
        in6_dev_put(ac->aca_idev);
        dst_release(&ac->aca_rt->dst);
        kfree(ac);
    }
}

/*
 *  device anycast group inc (add if not found)
 */
int ipv6_dev_ac_inc(struct net_device *dev, const struct in6_addr *addr)
{
    struct ifacaddr6 *aca;
    struct inet6_dev *idev;
    struct rt6_info *rt;
    int err;

    idev = in6_dev_get(dev);

    if (idev == NULL)
        return -EINVAL;

    write_lock_bh(&idev->lock);
    if (idev->dead) {
        err = -ENODEV;
        goto out;
    }

    for (aca = idev->ac_list; aca; aca = aca->aca_next) {
        if (ipv6_addr_equal(&aca->aca_addr, addr)) {
            aca->aca_users++;
            err = 0;
            goto out;
        }
    }

    /*
     *  not found: create a new one.
     */

    aca = kzalloc(sizeof(struct ifacaddr6), GFP_ATOMIC);

    if (aca == NULL) {
        err = -ENOMEM;
        goto out;
    }

    rt = addrconf_dst_alloc(idev, addr, true);
    if (IS_ERR(rt)) {
        kfree(aca);
        err = PTR_ERR(rt);
        goto out;
    }

    aca->aca_addr = *addr;
    aca->aca_idev = idev;
    aca->aca_rt = rt;
    aca->aca_users = 1;
    /* aca_tstamp should be updated upon changes */
    aca->aca_cstamp = aca->aca_tstamp = jiffies;
    atomic_set(&aca->aca_refcnt, 2);
    spin_lock_init(&aca->aca_lock);

    aca->aca_next = idev->ac_list;
    idev->ac_list = aca;
    write_unlock_bh(&idev->lock);

    ip6_ins_rt(rt);

    addrconf_join_solict(dev, &aca->aca_addr);

    aca_put(aca);
    return 0;
out:
    write_unlock_bh(&idev->lock);
    in6_dev_put(idev);
    return err;
}

/*
 *  device anycast group decrement
 */
int __ipv6_dev_ac_dec(struct inet6_dev *idev, const struct in6_addr *addr)
{
    struct ifacaddr6 *aca, *prev_aca;

    write_lock_bh(&idev->lock);
    prev_aca = NULL;
    for (aca = idev->ac_list; aca; aca = aca->aca_next) {
        if (ipv6_addr_equal(&aca->aca_addr, addr))
            break;
        prev_aca = aca;
    }
    if (!aca) {
        write_unlock_bh(&idev->lock);
        return -ENOENT;
    }
    if (--aca->aca_users > 0) {
        write_unlock_bh(&idev->lock);
        return 0;
    }
    if (prev_aca)
        prev_aca->aca_next = aca->aca_next;
    else
        idev->ac_list = aca->aca_next;
    write_unlock_bh(&idev->lock);
    addrconf_leave_solict(idev, &aca->aca_addr);

    dst_hold(&aca->aca_rt->dst);
    ip6_del_rt(aca->aca_rt);

    aca_put(aca);
    return 0;
}

/* called with rcu_read_lock() */
static int ipv6_dev_ac_dec(struct net_device *dev, const struct in6_addr *addr)
{
    struct inet6_dev *idev = __in6_dev_get(dev);

    if (idev == NULL)
        return -ENODEV;
    return __ipv6_dev_ac_dec(idev, addr);
}

/*
 *  check if the interface has this anycast address
 *  called with rcu_read_lock()
 */
static bool ipv6_chk_acast_dev(struct net_device *dev, const struct in6_addr *addr)
{
    struct inet6_dev *idev;
    struct ifacaddr6 *aca;

    idev = __in6_dev_get(dev);
    if (idev) {
        read_lock_bh(&idev->lock);
        for (aca = idev->ac_list; aca; aca = aca->aca_next)
            if (ipv6_addr_equal(&aca->aca_addr, addr))
                break;
        read_unlock_bh(&idev->lock);
        return aca != NULL;
    }
    return false;
}

/*
 *  check if given interface (or any, if dev==0) has this anycast address
 */
bool ipv6_chk_acast_addr(struct net *net, struct net_device *dev,
             const struct in6_addr *addr)
{
    bool found = false;

    rcu_read_lock();
    if (dev)
        found = ipv6_chk_acast_dev(dev, addr);
    else
        for_each_netdev_rcu(net, dev)
            if (ipv6_chk_acast_dev(dev, addr)) {
                found = true;
                break;
            }
    rcu_read_unlock();
    return found;
}


#ifdef CONFIG_PROC_FS
struct ac6_iter_state {
    struct seq_net_private p;
    struct net_device *dev;
    struct inet6_dev *idev;
};

#define ac6_seq_private(seq)    ((struct ac6_iter_state *)(seq)->private)

static inline struct ifacaddr6 *ac6_get_first(struct seq_file *seq)
{
    struct ifacaddr6 *im = NULL;
    struct ac6_iter_state *state = ac6_seq_private(seq);
    struct net *net = seq_file_net(seq);

    state->idev = NULL;
    for_each_netdev_rcu(net, state->dev) {
        struct inet6_dev *idev;
        idev = __in6_dev_get(state->dev);
        if (!idev)
            continue;
        read_lock_bh(&idev->lock);
        im = idev->ac_list;
        if (im) {
            state->idev = idev;
            break;
        }
        read_unlock_bh(&idev->lock);
    }
    return im;
}

static struct ifacaddr6 *ac6_get_next(struct seq_file *seq, struct ifacaddr6 *im)
{
    struct ac6_iter_state *state = ac6_seq_private(seq);

    im = im->aca_next;
    while (!im) {
        if (likely(state->idev != NULL))
            read_unlock_bh(&state->idev->lock);

        state->dev = next_net_device_rcu(state->dev);
        if (!state->dev) {
            state->idev = NULL;
            break;
        }
        state->idev = __in6_dev_get(state->dev);
        if (!state->idev)
            continue;
        read_lock_bh(&state->idev->lock);
        im = state->idev->ac_list;
    }
    return im;
}

static struct ifacaddr6 *ac6_get_idx(struct seq_file *seq, loff_t pos)
{
    struct ifacaddr6 *im = ac6_get_first(seq);
    if (im)
        while (pos && (im = ac6_get_next(seq, im)) != NULL)
            --pos;
    return pos ? NULL : im;
}

static void *ac6_seq_start(struct seq_file *seq, loff_t *pos)
    __acquires(RCU)
{
    rcu_read_lock();
    return ac6_get_idx(seq, *pos);
}

static void *ac6_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct ifacaddr6 *im = ac6_get_next(seq, v);

    ++*pos;
    return im;
}

static void ac6_seq_stop(struct seq_file *seq, void *v)
    __releases(RCU)
{
    struct ac6_iter_state *state = ac6_seq_private(seq);

    if (likely(state->idev != NULL)) {
        read_unlock_bh(&state->idev->lock);
        state->idev = NULL;
    }
    rcu_read_unlock();
}

static int ac6_seq_show(struct seq_file *seq, void *v)
{
    struct ifacaddr6 *im = (struct ifacaddr6 *)v;
    struct ac6_iter_state *state = ac6_seq_private(seq);

    seq_printf(seq, "%-4d %-15s %pi6 %5d\n",
           state->dev->ifindex, state->dev->name,
           &im->aca_addr, im->aca_users);
    return 0;
}

static const struct seq_operations ac6_seq_ops = {
    .start  =   ac6_seq_start,
    .next   =   ac6_seq_next,
    .stop   =   ac6_seq_stop,
    .show   =   ac6_seq_show,
};

static int ac6_seq_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &ac6_seq_ops,
                sizeof(struct ac6_iter_state));
}

static const struct file_operations ac6_seq_fops = {
    .owner      =   THIS_MODULE,
    .open       =   ac6_seq_open,
    .read       =   seq_read,
    .llseek     =   seq_lseek,
    .release    =   seq_release_net,
};

int __net_init ac6_proc_init(struct net *net)
{
    if (!proc_net_fops_create(net, "anycast6", S_IRUGO, &ac6_seq_fops))
        return -ENOMEM;

    return 0;
}

void ac6_proc_exit(struct net *net)
{
    proc_net_remove(net, "anycast6");
}
#endif