// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/lockd/host.c
 *
 * Management for NLM peer hosts. The nlm_host struct is shared
 * between client and server implementation. The only reason to
 * do so is to reduce code bloat.
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/mutex.h>

#include <linux/sunrpc/svc_xprt.h>

#include <net/ipv6.h>

#include "netns.h"

#define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
#define NLM_HOST_NRHASH         32
#define NLM_HOST_REBIND         (60 * HZ)
#define NLM_HOST_EXPIRE         (300 * HZ)
#define NLM_HOST_COLLECT        (120 * HZ)

static struct hlist_head        nlm_server_hosts[NLM_HOST_NRHASH];
static struct hlist_head        nlm_client_hosts[NLM_HOST_NRHASH];

#define for_each_host(host, chain, table) \
        for ((chain) = (table); \
             (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
                hlist_for_each_entry((host), (chain), h_hash)

#define for_each_host_safe(host, next, chain, table) \
        for ((chain) = (table); \
             (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
                hlist_for_each_entry_safe((host), (next), \
                                                (chain), h_hash)

static unsigned long            nrhosts;
static DEFINE_MUTEX(nlm_host_mutex);

static void                     nlm_gc_hosts(struct net *net);

struct nlm_lookup_host_info {
        const int               server;         /* search for server|client */
        const struct sockaddr   *sap;           /* address to search for */
        const size_t            salen;          /* it's length */
        const unsigned short    protocol;       /* transport to search for*/
        const u32               version;        /* NLM version to search for */
        const char              *hostname;      /* remote's hostname */
        const size_t            hostname_len;   /* it's length */
        const int               noresvport;     /* use non-priv port */
        struct net              *net;           /* network namespace to bind */
        const struct cred       *cred;
};

/*
 * Hash function must work well on big- and little-endian platforms
 */
static unsigned int __nlm_hash32(const __be32 n)
{
        unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
        return hash ^ (hash >> 8);
}

static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
{
        const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
        return __nlm_hash32(sin->sin_addr.s_addr);
}

static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
{
        const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
        const struct in6_addr addr = sin6->sin6_addr;
        return __nlm_hash32(addr.s6_addr32[0]) ^
               __nlm_hash32(addr.s6_addr32[1]) ^
               __nlm_hash32(addr.s6_addr32[2]) ^
               __nlm_hash32(addr.s6_addr32[3]);
}

static unsigned int nlm_hash_address(const struct sockaddr *sap)
{
        unsigned int hash;

        switch (sap->sa_family) {
        case AF_INET:
                hash = __nlm_hash_addr4(sap);
                break;
        case AF_INET6:
                hash = __nlm_hash_addr6(sap);
                break;
        default:
                hash = 0;
        }
        return hash & (NLM_HOST_NRHASH - 1);
}

/*
 * Allocate and initialize an nlm_host.  Common to both client and server.
 */
static struct nlm_host *nlm_alloc_host(struct nlm_lookup_host_info *ni,
                                       struct nsm_handle *nsm)
{
        struct nlm_host *host = NULL;
        unsigned long now = jiffies;

        if (nsm != NULL)
                refcount_inc(&nsm->sm_count);
        else {
                nsm = nsm_get_handle(ni->net, ni->sap, ni->salen,
                                        ni->hostname, ni->hostname_len);
                if (unlikely(nsm == NULL)) {
                        dprintk("lockd: %s failed; no nsm handle\n",
                                __func__);
                        goto out;
                }
        }

        host = kmalloc_obj(*host);
        if (unlikely(host == NULL)) {
                dprintk("lockd: %s failed; no memory\n", __func__);
                nsm_release(nsm);
                goto out;
        }

        memcpy(nlm_addr(host), ni->sap, ni->salen);
        host->h_addrlen    = ni->salen;
        rpc_set_port(nlm_addr(host), 0);
        host->h_srcaddrlen = 0;

        host->h_rpcclnt    = NULL;
        host->h_name       = nsm->sm_name;
        host->h_version    = ni->version;
        host->h_proto      = ni->protocol;
        host->h_reclaiming = 0;
        host->h_server     = ni->server;
        host->h_noresvport = ni->noresvport;
        host->h_inuse      = 0;
        init_waitqueue_head(&host->h_gracewait);
        init_rwsem(&host->h_rwsem);
        host->h_state      = 0;
        host->h_nsmstate   = 0;
        host->h_pidcount   = 0;
        refcount_set(&host->h_count, 1);
        mutex_init(&host->h_mutex);
        host->h_nextrebind = now + NLM_HOST_REBIND;
        host->h_expires    = now + NLM_HOST_EXPIRE;
        INIT_LIST_HEAD(&host->h_lockowners);
        spin_lock_init(&host->h_lock);
        INIT_LIST_HEAD(&host->h_granted);
        INIT_LIST_HEAD(&host->h_reclaim);
        host->h_nsmhandle  = nsm;
        host->h_addrbuf    = nsm->sm_addrbuf;
        host->net          = ni->net;
        host->h_cred       = get_cred(ni->cred);
        strscpy(host->nodename, utsname()->nodename, sizeof(host->nodename));

out:
        return host;
}

/*
 * Destroy an nlm_host and free associated resources
 *
 * Caller must hold nlm_host_mutex.
 */
static void nlm_destroy_host_locked(struct nlm_host *host)
{
        struct rpc_clnt *clnt;
        struct lockd_net *ln = net_generic(host->net, lockd_net_id);

        dprintk("lockd: destroy host %s\n", host->h_name);

        hlist_del_init(&host->h_hash);

        nsm_unmonitor(host);
        nsm_release(host->h_nsmhandle);

        clnt = host->h_rpcclnt;
        if (clnt != NULL)
                rpc_shutdown_client(clnt);
        put_cred(host->h_cred);
        kfree(host);

        ln->nrhosts--;
        nrhosts--;
}

/**
 * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 * @sap: network address of server
 * @salen: length of server address
 * @protocol: transport protocol to use
 * @version: NLM protocol version
 * @hostname: '\0'-terminated hostname of server
 * @noresvport: 1 if non-privileged port should be used
 * @net: pointer to net namespace
 * @cred: pointer to cred
 *
 * Returns an nlm_host structure that matches the passed-in
 * [server address, transport protocol, NLM version, server hostname].
 * If one doesn't already exist in the host cache, a new handle is
 * created and returned.
 */
struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
                                     const size_t salen,
                                     const unsigned short protocol,
                                     const u32 version,
                                     const char *hostname,
                                     int noresvport,
                                     struct net *net,
                                     const struct cred *cred)
{
        struct nlm_lookup_host_info ni = {
                .server         = 0,
                .sap            = sap,
                .salen          = salen,
                .protocol       = protocol,
                .version        = version,
                .hostname       = hostname,
                .hostname_len   = strlen(hostname),
                .noresvport     = noresvport,
                .net            = net,
                .cred           = cred,
        };
        struct hlist_head *chain;
        struct nlm_host *host;
        struct nsm_handle *nsm = NULL;
        struct lockd_net *ln = net_generic(net, lockd_net_id);

        dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
                        (hostname ? hostname : "<none>"), version,
                        (protocol == IPPROTO_UDP ? "udp" : "tcp"));

        mutex_lock(&nlm_host_mutex);

        chain = &nlm_client_hosts[nlm_hash_address(sap)];
        hlist_for_each_entry(host, chain, h_hash) {
                if (host->net != net)
                        continue;
                if (!rpc_cmp_addr(nlm_addr(host), sap))
                        continue;

                /* Same address. Share an NSM handle if we already have one */
                if (nsm == NULL)
                        nsm = host->h_nsmhandle;

                if (host->h_proto != protocol)
                        continue;
                if (host->h_version != version)
                        continue;

                nlm_get_host(host);
                dprintk("lockd: %s found host %s (%s)\n", __func__,
                        host->h_name, host->h_addrbuf);
                goto out;
        }

        host = nlm_alloc_host(&ni, nsm);
        if (unlikely(host == NULL))
                goto out;

        hlist_add_head(&host->h_hash, chain);
        ln->nrhosts++;
        nrhosts++;

        dprintk("lockd: %s created host %s (%s)\n", __func__,
                host->h_name, host->h_addrbuf);

out:
        mutex_unlock(&nlm_host_mutex);
        return host;
}

/**
 * nlmclnt_release_host - release client nlm_host
 * @host: nlm_host to release
 *
 */
void nlmclnt_release_host(struct nlm_host *host)
{
        if (host == NULL)
                return;

        dprintk("lockd: release client host %s\n", host->h_name);

        WARN_ON_ONCE(host->h_server);

        if (refcount_dec_and_mutex_lock(&host->h_count, &nlm_host_mutex)) {
                WARN_ON_ONCE(!list_empty(&host->h_lockowners));
                WARN_ON_ONCE(!list_empty(&host->h_granted));
                WARN_ON_ONCE(!list_empty(&host->h_reclaim));

                nlm_destroy_host_locked(host);
                mutex_unlock(&nlm_host_mutex);
        }
}

/**
 * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 * @rqstp: incoming NLM request
 * @hostname: name of client host
 * @hostname_len: length of client hostname
 *
 * Returns an nlm_host structure that matches the [client address,
 * transport protocol, NLM version, client hostname] of the passed-in
 * NLM request.  If one doesn't already exist in the host cache, a
 * new handle is created and returned.
 *
 * Before possibly creating a new nlm_host, construct a sockaddr
 * for a specific source address in case the local system has
 * multiple network addresses.  The family of the address in
 * rq_daddr is guaranteed to be the same as the family of the
 * address in rq_addr, so it's safe to use the same family for
 * the source address.
 */
struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
                                    const char *hostname,
                                    const size_t hostname_len)
{
        struct hlist_head *chain;
        struct nlm_host *host = NULL;
        struct nsm_handle *nsm = NULL;
        struct sockaddr *src_sap = svc_daddr(rqstp);
        size_t src_len = rqstp->rq_daddrlen;
        struct net *net = SVC_NET(rqstp);
        struct nlm_lookup_host_info ni = {
                .server         = 1,
                .sap            = svc_addr(rqstp),
                .salen          = rqstp->rq_addrlen,
                .protocol       = rqstp->rq_prot,
                .version        = rqstp->rq_vers,
                .hostname       = hostname,
                .hostname_len   = hostname_len,
                .net            = net,
        };
        struct lockd_net *ln = net_generic(net, lockd_net_id);

        dprintk("lockd: %s(host='%.*s', vers=%u, proto=%s)\n", __func__,
                        (int)hostname_len, hostname, rqstp->rq_vers,
                        (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));

        mutex_lock(&nlm_host_mutex);

        if (time_after_eq(jiffies, ln->next_gc))
                nlm_gc_hosts(net);

        chain = &nlm_server_hosts[nlm_hash_address(ni.sap)];
        hlist_for_each_entry(host, chain, h_hash) {
                if (host->net != net)
                        continue;
                if (!rpc_cmp_addr(nlm_addr(host), ni.sap))
                        continue;

                /* Same address. Share an NSM handle if we already have one */
                if (nsm == NULL)
                        nsm = host->h_nsmhandle;

                if (host->h_proto != ni.protocol)
                        continue;
                if (host->h_version != ni.version)
                        continue;
                if (!rpc_cmp_addr(nlm_srcaddr(host), src_sap))
                        continue;

                /* Move to head of hash chain. */
                hlist_del(&host->h_hash);
                hlist_add_head(&host->h_hash, chain);

                nlm_get_host(host);
                dprintk("lockd: %s found host %s (%s)\n",
                        __func__, host->h_name, host->h_addrbuf);
                goto out;
        }

        host = nlm_alloc_host(&ni, nsm);
        if (unlikely(host == NULL))
                goto out;

        memcpy(nlm_srcaddr(host), src_sap, src_len);
        host->h_srcaddrlen = src_len;
        hlist_add_head(&host->h_hash, chain);
        ln->nrhosts++;
        nrhosts++;

        refcount_inc(&host->h_count);

        dprintk("lockd: %s created host %s (%s)\n",
                __func__, host->h_name, host->h_addrbuf);

out:
        mutex_unlock(&nlm_host_mutex);
        return host;
}

/**
 * nlmsvc_release_host - release server nlm_host
 * @host: nlm_host to release
 *
 * Host is destroyed later in nlm_gc_host().
 */
void nlmsvc_release_host(struct nlm_host *host)
{
        if (host == NULL)
                return;

        dprintk("lockd: release server host %s\n", host->h_name);

        WARN_ON_ONCE(!host->h_server);
        refcount_dec(&host->h_count);
}

/*
 * Create the NLM RPC client for an NLM peer
 */
struct rpc_clnt *
nlm_bind_host(struct nlm_host *host)
{
        struct rpc_clnt *clnt;

        dprintk("lockd: nlm_bind_host %s (%s)\n",
                        host->h_name, host->h_addrbuf);

        /* Lock host handle */
        mutex_lock(&host->h_mutex);

        /* If we've already created an RPC client, check whether
         * RPC rebind is required
         */
        if ((clnt = host->h_rpcclnt) != NULL) {
                nlm_rebind_host(host);
        } else {
                unsigned long increment = nlm_timeout * HZ;
                struct rpc_timeout timeparms = {
                        .to_initval     = increment,
                        .to_increment   = increment,
                        .to_maxval      = increment * 6UL,
                        .to_retries     = 5U,
                };
                struct rpc_create_args args = {
                        .net            = host->net,
                        .protocol       = host->h_proto,
                        .address        = nlm_addr(host),
                        .addrsize       = host->h_addrlen,
                        .timeout        = &timeparms,
                        .servername     = host->h_name,
                        .program        = &nlm_program,
                        .version        = host->h_version,
                        .authflavor     = RPC_AUTH_UNIX,
                        .flags          = (RPC_CLNT_CREATE_NOPING |
                                           RPC_CLNT_CREATE_AUTOBIND |
                                           RPC_CLNT_CREATE_REUSEPORT),
                        .cred           = host->h_cred,
                };

                /*
                 * lockd retries server side blocks automatically so we want
                 * those to be soft RPC calls. Client side calls need to be
                 * hard RPC tasks.
                 */
                if (!host->h_server)
                        args.flags |= RPC_CLNT_CREATE_HARDRTRY;
                if (host->h_noresvport)
                        args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
                if (host->h_srcaddrlen)
                        args.saddress = nlm_srcaddr(host);

                clnt = rpc_create(&args);
                if (!IS_ERR(clnt))
                        host->h_rpcclnt = clnt;
                else {
                        printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
                        clnt = NULL;
                }
        }

        mutex_unlock(&host->h_mutex);
        return clnt;
}

/**
 * nlm_rebind_host - If needed, force a portmap lookup of the peer's lockd port
 * @host: NLM host handle for peer
 *
 * This is not needed when using a connection-oriented protocol, such as TCP.
 * The existing autobind mechanism is sufficient to force a rebind when
 * required, e.g. on connection state transitions.
 */
void
nlm_rebind_host(struct nlm_host *host)
{
        if (host->h_proto != IPPROTO_UDP)
                return;

        if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
                rpc_force_rebind(host->h_rpcclnt);
                host->h_nextrebind = jiffies + NLM_HOST_REBIND;
        }
}

/*
 * Increment NLM host count
 */
struct nlm_host * nlm_get_host(struct nlm_host *host)
{
        if (host) {
                dprintk("lockd: get host %s\n", host->h_name);
                refcount_inc(&host->h_count);
                host->h_expires = jiffies + NLM_HOST_EXPIRE;
        }
        return host;
}

static struct nlm_host *next_host_state(struct hlist_head *cache,
                                        struct nsm_handle *nsm,
                                        const struct nlm_reboot *info)
{
        struct nlm_host *host;
        struct hlist_head *chain;

        mutex_lock(&nlm_host_mutex);
        for_each_host(host, chain, cache) {
                if (host->h_nsmhandle == nsm
                    && host->h_nsmstate != info->state) {
                        host->h_nsmstate = info->state;
                        host->h_state++;

                        nlm_get_host(host);
                        mutex_unlock(&nlm_host_mutex);
                        return host;
                }
        }

        mutex_unlock(&nlm_host_mutex);
        return NULL;
}

/**
 * nlm_host_rebooted - Release all resources held by rebooted host
 * @net:  network namespace
 * @info: pointer to decoded results of NLM_SM_NOTIFY call
 *
 * We were notified that the specified host has rebooted.  Release
 * all resources held by that peer.
 */
void nlm_host_rebooted(const struct net *net, const struct nlm_reboot *info)
{
        struct nsm_handle *nsm;
        struct nlm_host *host;

        nsm = nsm_reboot_lookup(net, info);
        if (unlikely(nsm == NULL))
                return;

        /* Mark all hosts tied to this NSM state as having rebooted.
         * We run the loop repeatedly, because we drop the host table
         * lock for this.
         * To avoid processing a host several times, we match the nsmstate.
         */
        while ((host = next_host_state(nlm_server_hosts, nsm, info)) != NULL) {
                nlmsvc_free_host_resources(host);
                nlmsvc_release_host(host);
        }
        while ((host = next_host_state(nlm_client_hosts, nsm, info)) != NULL) {
                nlmclnt_recovery(host);
                nlmclnt_release_host(host);
        }

        nsm_release(nsm);
}

static void nlm_complain_hosts(struct net *net)
{
        struct hlist_head *chain;
        struct nlm_host *host;

        if (net) {
                struct lockd_net *ln = net_generic(net, lockd_net_id);

                if (ln->nrhosts == 0)
                        return;
                pr_warn("lockd: couldn't shutdown host module for net %x!\n",
                        net->ns.inum);
                dprintk("lockd: %lu hosts left in net %x:\n", ln->nrhosts,
                        net->ns.inum);
        } else {
                if (nrhosts == 0)
                        return;
                printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
                dprintk("lockd: %lu hosts left:\n", nrhosts);
        }

        for_each_host(host, chain, nlm_server_hosts) {
                if (net && host->net != net)
                        continue;
                dprintk("       %s (cnt %d use %d exp %ld net %x)\n",
                        host->h_name, refcount_read(&host->h_count),
                        host->h_inuse, host->h_expires, host->net->ns.inum);
        }
}

void
nlm_shutdown_hosts_net(struct net *net)
{
        struct hlist_head *chain;
        struct nlm_host *host;

        mutex_lock(&nlm_host_mutex);

        /* First, make all hosts eligible for gc */
        dprintk("lockd: nuking all hosts in net %x...\n",
                net ? net->ns.inum : 0);
        for_each_host(host, chain, nlm_server_hosts) {
                if (net && host->net != net)
                        continue;
                host->h_expires = jiffies - 1;
                if (host->h_rpcclnt) {
                        rpc_shutdown_client(host->h_rpcclnt);
                        host->h_rpcclnt = NULL;
                }
                nlmsvc_free_host_resources(host);
        }

        /* Then, perform a garbage collection pass */
        nlm_gc_hosts(net);
        nlm_complain_hosts(net);
        mutex_unlock(&nlm_host_mutex);
}

/*
 * Shut down the hosts module.
 * Note that this routine is called only at server shutdown time.
 */
void
nlm_shutdown_hosts(void)
{
        dprintk("lockd: shutting down host module\n");
        nlm_shutdown_hosts_net(NULL);
}

/*
 * Garbage collect any unused NLM hosts.
 * This GC combines reference counting for async operations with
 * mark & sweep for resources held by remote clients.
 */
static void
nlm_gc_hosts(struct net *net)
{
        struct hlist_head *chain;
        struct hlist_node *next;
        struct nlm_host *host;

        dprintk("lockd: host garbage collection for net %x\n",
                net ? net->ns.inum : 0);
        for_each_host(host, chain, nlm_server_hosts) {
                if (net && host->net != net)
                        continue;
                host->h_inuse = 0;
        }

        /* Mark all hosts that hold locks, blocks or shares */
        nlmsvc_mark_resources(net);

        for_each_host_safe(host, next, chain, nlm_server_hosts) {
                if (net && host->net != net)
                        continue;
                if (host->h_inuse || time_before(jiffies, host->h_expires)) {
                        dprintk("nlm_gc_hosts skipping %s "
                                "(cnt %d use %d exp %ld net %x)\n",
                                host->h_name, refcount_read(&host->h_count),
                                host->h_inuse, host->h_expires,
                                host->net->ns.inum);
                        continue;
                }
                if (refcount_dec_if_one(&host->h_count))
                        nlm_destroy_host_locked(host);
        }

        if (net) {
                struct lockd_net *ln = net_generic(net, lockd_net_id);

                ln->next_gc = jiffies + NLM_HOST_COLLECT;
        }
}