/*      $NetBSD: ip_flow.c,v 1.87 2025/12/10 21:33:03 andvar Exp $      */

/*-
 * Copyright (c) 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by the 3am Software Foundry ("3am").  It was developed by Matt Thomas.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip_flow.c,v 1.87 2025/12/10 21:33:03 andvar Exp $");

#ifdef _KERNEL_OPT
#include "opt_net_mpsafe.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/pool.h>
#include <sys/sysctl.h>
#include <sys/workqueue.h>
#include <sys/atomic.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/route.h>
#include <net/pfil.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/ip_private.h>

/*
 * Similar code is very well commented in netinet6/ip6_flow.c
 */

#define IPFLOW_HASHBITS         6       /* should not be a multiple of 8 */

static struct pool ipflow_pool;

TAILQ_HEAD(ipflowhead, ipflow);

#define IPFLOW_TIMER            (5 * PR_SLOWHZ)
#define IPFLOW_DEFAULT_HASHSIZE (1 << IPFLOW_HASHBITS)

/*
 * ip_flow.c internal lock.
 * If we use softnet_lock, it would cause recursive lock.
 *
 * This is a tentative workaround.
 * We should make it scalable somehow in the future.
 */
static kmutex_t ipflow_lock;
static struct ipflowhead *ipflowtable = NULL;
static struct ipflowhead ipflowlist;
static int ipflow_inuse;

#define IPFLOW_INSERT(hashidx, ipf) \
do { \
        (ipf)->ipf_hashidx = (hashidx); \
        TAILQ_INSERT_HEAD(&ipflowtable[(hashidx)], (ipf), ipf_hash); \
        TAILQ_INSERT_HEAD(&ipflowlist, (ipf), ipf_list); \
} while (/*CONSTCOND*/ 0)

#define IPFLOW_REMOVE(hashidx, ipf) \
do { \
        TAILQ_REMOVE(&ipflowtable[(hashidx)], (ipf), ipf_hash); \
        TAILQ_REMOVE(&ipflowlist, (ipf), ipf_list); \
} while (/*CONSTCOND*/ 0)

#ifndef IPFLOW_MAX
#define IPFLOW_MAX              256
#endif
static int ip_maxflows = IPFLOW_MAX;
static int ip_hashsize = IPFLOW_DEFAULT_HASHSIZE;

static struct ipflow *ipflow_reap(bool);
static void ipflow_sysctl_init(struct sysctllog **);

static void ipflow_slowtimo_work(struct work *, void *);
static struct workqueue *ipflow_slowtimo_wq;
static struct work      ipflow_slowtimo_wk;

static size_t
ipflow_hash(const struct ip *ip)
{
        size_t hash = ip->ip_tos;
        size_t idx;

        for (idx = 0; idx < 32; idx += IPFLOW_HASHBITS) {
                hash += (ip->ip_dst.s_addr >> (32 - idx)) +
                    (ip->ip_src.s_addr >> idx);
        }

        return hash & (ip_hashsize-1);
}

static struct ipflow *
ipflow_lookup(const struct ip *ip)
{
        size_t hash;
        struct ipflow *ipf;

        KASSERT(mutex_owned(&ipflow_lock));

        hash = ipflow_hash(ip);

        TAILQ_FOREACH(ipf, &ipflowtable[hash], ipf_hash) {
                if (ip->ip_dst.s_addr == ipf->ipf_dst.s_addr
                    && ip->ip_src.s_addr == ipf->ipf_src.s_addr
                    && ip->ip_tos == ipf->ipf_tos)
                        break;
        }
        return ipf;
}

void
ipflow_poolinit(void)
{

        pool_init(&ipflow_pool, sizeof(struct ipflow), 0, 0, 0, "ipflowpl",
            NULL, IPL_NET);
}

static int
ipflow_reinit(int table_size)
{
        struct ipflowhead *new_table;
        size_t i;

        KASSERT(mutex_owned(&ipflow_lock));

        new_table = (struct ipflowhead *)malloc(sizeof(struct ipflowhead) *
            table_size, M_RTABLE, M_NOWAIT);

        if (new_table == NULL)
                return 1;

        if (ipflowtable != NULL)
                free(ipflowtable, M_RTABLE);

        ipflowtable = new_table;
        ip_hashsize = table_size;

        TAILQ_INIT(&ipflowlist);
        for (i = 0; i < ip_hashsize; i++)
                TAILQ_INIT(&ipflowtable[i]);

        return 0;
}

void
ipflow_init(void)
{
        int error;

        error = workqueue_create(&ipflow_slowtimo_wq, "ipflow_slowtimo",
            ipflow_slowtimo_work, NULL, PRI_SOFTNET, IPL_SOFTNET, WQ_MPSAFE);
        if (error != 0)
                panic("%s: workqueue_create failed (%d)\n", __func__, error);

        mutex_init(&ipflow_lock, MUTEX_DEFAULT, IPL_NONE);

        mutex_enter(&ipflow_lock);
        (void)ipflow_reinit(ip_hashsize);
        mutex_exit(&ipflow_lock);
        ipflow_sysctl_init(NULL);
}

int
ipflow_fastforward(struct mbuf *m)
{
        struct ip *ip;
        struct ip ip_store;
        struct ipflow *ipf;
        struct rtentry *rt = NULL;
        const struct sockaddr *dst;
        int error;
        int iplen;
        struct ifnet *ifp;
        int s;
        int ret = 0;

        mutex_enter(&ipflow_lock);
        /*
         * Are we forwarding packets?  Big enough for an IP packet?
         */
        if (!ipforwarding || ipflow_inuse == 0 || m->m_len < sizeof(struct ip))
                goto out;

        /*
         * Was packet received as a link-level multicast or broadcast?
         * If so, don't try to fast forward..
         */
        if ((m->m_flags & (M_BCAST|M_MCAST)) != 0)
                goto out;

        /*
         * IP header with no option and valid version and length
         */
        ip = mtod(m, struct ip *);
        if (!ACCESSIBLE_POINTER(ip, struct ip)) {
                memcpy(&ip_store, mtod(m, const void *), sizeof(ip_store));
                ip = &ip_store;
        }
        iplen = ntohs(ip->ip_len);
        if (ip->ip_v != IPVERSION || ip->ip_hl != (sizeof(struct ip) >> 2) ||
            iplen < sizeof(struct ip) || iplen > m->m_pkthdr.len)
                goto out;
        /*
         * Find a flow.
         */
        if ((ipf = ipflow_lookup(ip)) == NULL)
                goto out;

        ifp = m_get_rcvif(m, &s);
        if (__predict_false(ifp == NULL))
                goto out_unref;
        /*
         * Verify the IP header checksum.
         */
        switch (m->m_pkthdr.csum_flags &
                ((ifp->if_csum_flags_rx & M_CSUM_IPv4) |
                 M_CSUM_IPv4_BAD)) {
        case M_CSUM_IPv4|M_CSUM_IPv4_BAD:
                m_put_rcvif(ifp, &s);
                goto out_unref;

        case M_CSUM_IPv4:
                /* Checksum was okay. */
                break;

        default:
                /* Must compute it ourselves. */
                if (in_cksum(m, sizeof(struct ip)) != 0) {
                        m_put_rcvif(ifp, &s);
                        goto out_unref;
                }
                break;
        }
        m_put_rcvif(ifp, &s);

        /*
         * Route and interface still up?
         */
        rt = rtcache_validate(&ipf->ipf_ro);
        if (rt == NULL || (rt->rt_ifp->if_flags & IFF_UP) == 0 ||
            (rt->rt_flags & (RTF_BLACKHOLE | RTF_BROADCAST)) != 0)
                goto out_unref;

        /*
         * Packet size OK?  TTL?
         */
        if (m->m_pkthdr.len > rt->rt_ifp->if_mtu || ip->ip_ttl <= IPTTLDEC)
                goto out_unref;

        /*
         * Clear any in-bound checksum flags for this packet.
         */
        m->m_pkthdr.csum_flags = 0;

        /*
         * Everything checks out and so we can forward this packet.
         * Modify the TTL and incrementally change the checksum.
         *
         * This method of adding the checksum works on either endian CPU.
         * If htons() is inlined, all the arithmetic is folded; otherwise
         * the htons()s are combined by CSE due to the const attribute.
         *
         * Don't bother using HW checksumming here -- the incremental
         * update is pretty fast.
         */
        ip->ip_ttl -= IPTTLDEC;
        if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
                ip->ip_sum -= ~htons(IPTTLDEC << 8);
        else
                ip->ip_sum += htons(IPTTLDEC << 8);

        /*
         * Done modifying the header; copy it back, if necessary.
         *
         * XXX Use m_copyback_cow(9) here? --dyoung
         */
        if (!ACCESSIBLE_POINTER(mtod(m, void *), struct ip))
                memcpy(mtod(m, void *), &ip_store, sizeof(ip_store));

        /*
         * Trim the packet in case it's too long..
         */
        if (m->m_pkthdr.len > iplen) {
                if (m->m_len == m->m_pkthdr.len) {
                        m->m_len = iplen;
                        m->m_pkthdr.len = iplen;
                } else
                        m_adj(m, iplen - m->m_pkthdr.len);
        }

        /*
         * Send the packet on its way.  All we can get back is ENOBUFS
         */
        ipf->ipf_uses++;

#if 0
        /*
         * Sorting list is too heavy for fast path(packet processing path).
         * It degrades about 10% performance. So, we does not sort ipflowtable,
         * and then we use FIFO cache replacement instead fo LRU.
         */
        /* move to head (LRU) for ipflowlist. ipflowtable ooes not care LRU. */
        TAILQ_REMOVE(&ipflowlist, ipf, ipf_list);
        TAILQ_INSERT_HEAD(&ipflowlist, ipf, ipf_list);
#endif

        PRT_SLOW_ARM(ipf->ipf_timer, IPFLOW_TIMER);

        if (rt->rt_flags & RTF_GATEWAY)
                dst = rt->rt_gateway;
        else
                dst = rtcache_getdst(&ipf->ipf_ro);

        if ((error = if_output_lock(rt->rt_ifp, rt->rt_ifp, m, dst, rt)) != 0) {
                if (error == ENOBUFS)
                        ipf->ipf_dropped++;
                else
                        ipf->ipf_errors++;
        }
        ret = 1;
out_unref:
        rtcache_unref(rt, &ipf->ipf_ro);
out:
        mutex_exit(&ipflow_lock);
        return ret;
}

static void
ipflow_addstats(struct ipflow *ipf)
{
        struct rtentry *rt;
        net_stat_ref_t ips;

        rt = rtcache_validate(&ipf->ipf_ro);
        if (rt != NULL) {
                rt->rt_use += ipf->ipf_uses;
                rtcache_unref(rt, &ipf->ipf_ro);
        }

        ips = IP_STAT_GETREF();
        _NET_STATADD_REF(ips, IP_STAT_CANTFORWARD,
            ipf->ipf_errors + ipf->ipf_dropped);
        _NET_STATADD_REF(ips, IP_STAT_TOTAL, ipf->ipf_uses);
        _NET_STATADD_REF(ips, IP_STAT_FORWARD, ipf->ipf_uses);
        _NET_STATADD_REF(ips, IP_STAT_FASTFORWARD, ipf->ipf_uses);
        IP_STAT_PUTREF();
}

static void
ipflow_free(struct ipflow *ipf)
{

        KASSERT(mutex_owned(&ipflow_lock));

        /*
         * Remove the flow from the hash table (at elevated IPL).
         * Once it's off the list, we can deal with it at normal
         * network IPL.
         */
        IPFLOW_REMOVE(ipf->ipf_hashidx, ipf);

        ipflow_addstats(ipf);
        rtcache_free(&ipf->ipf_ro);
        ipflow_inuse--;
        pool_put(&ipflow_pool, ipf);
}

static struct ipflow *
ipflow_reap(bool just_one)
{
        struct ipflow *ipf;

        KASSERT(mutex_owned(&ipflow_lock));

        /*
         * This case must remove one ipflow. Furthermore, this case is used in
         * fast path(packet processing path). So, simply remove TAILQ_LAST one.
         */
        if (just_one) {
                ipf = TAILQ_LAST(&ipflowlist, ipflowhead);
                KASSERT(ipf != NULL);

                IPFLOW_REMOVE(ipf->ipf_hashidx, ipf);

                ipflow_addstats(ipf);
                rtcache_free(&ipf->ipf_ro);
                return ipf;
        }

        /*
         * This case is used in slow path(sysctl).
         * At first, remove invalid rtcache ipflow, and then remove TAILQ_LAST
         * ipflow if it is ensured least recently used by comparing last_uses.
         */
        while (ipflow_inuse > ip_maxflows) {
                struct ipflow *maybe_ipf = TAILQ_LAST(&ipflowlist, ipflowhead);

                TAILQ_FOREACH(ipf, &ipflowlist, ipf_list) {
                        struct rtentry *rt;
                        /*
                         * If this no longer points to a valid route
                         * reclaim it.
                         */
                        rt = rtcache_validate(&ipf->ipf_ro);
                        if (rt == NULL)
                                goto done;
                        rtcache_unref(rt, &ipf->ipf_ro);
                        /*
                         * choose the one that's been least recently
                         * used or has had the least uses in the
                         * last 1.5 intervals.
                         */
                        if (ipf->ipf_timer < maybe_ipf->ipf_timer
                            || ((ipf->ipf_timer == maybe_ipf->ipf_timer)
                                && (ipf->ipf_last_uses + ipf->ipf_uses
                                    < maybe_ipf->ipf_last_uses + maybe_ipf->ipf_uses)))
                                maybe_ipf = ipf;
                }
                ipf = maybe_ipf;
            done:
                /*
                 * Remove the entry from the flow table.
                 */
                IPFLOW_REMOVE(ipf->ipf_hashidx, ipf);

                ipflow_addstats(ipf);
                rtcache_free(&ipf->ipf_ro);
                pool_put(&ipflow_pool, ipf);
                ipflow_inuse--;
        }
        return NULL;
}

static unsigned int ipflow_work_enqueued = 0;

static void
ipflow_slowtimo_work(struct work *wk, void *arg)
{
        struct rtentry *rt;
        struct ipflow *ipf, *next_ipf;
        net_stat_ref_t ips;

        /* We can allow enqueuing another work at this point */
        atomic_swap_uint(&ipflow_work_enqueued, 0);

        SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
        mutex_enter(&ipflow_lock);
        for (ipf = TAILQ_FIRST(&ipflowlist); ipf != NULL; ipf = next_ipf) {
                next_ipf = TAILQ_NEXT(ipf, ipf_list);
                if (PRT_SLOW_ISEXPIRED(ipf->ipf_timer) ||
                    (rt = rtcache_validate(&ipf->ipf_ro)) == NULL) {
                        ipflow_free(ipf);
                } else {
                        ipf->ipf_last_uses = ipf->ipf_uses;
                        rt->rt_use += ipf->ipf_uses;
                        rtcache_unref(rt, &ipf->ipf_ro);
                        ips = IP_STAT_GETREF();
                        _NET_STATADD_REF(ips, IP_STAT_TOTAL, ipf->ipf_uses);
                        _NET_STATADD_REF(ips, IP_STAT_FORWARD, ipf->ipf_uses);
                        _NET_STATADD_REF(ips, IP_STAT_FASTFORWARD,
                            ipf->ipf_uses);
                        IP_STAT_PUTREF();
                        ipf->ipf_uses = 0;
                }
        }
        mutex_exit(&ipflow_lock);
        SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

void
ipflow_slowtimo(void)
{

        /* Avoid enqueuing another work when one is already enqueued */
        if (atomic_swap_uint(&ipflow_work_enqueued, 1) == 1)
                return;

        workqueue_enqueue(ipflow_slowtimo_wq, &ipflow_slowtimo_wk, NULL);
}

void
ipflow_create(struct route *ro, struct mbuf *m)
{
        const struct ip *const ip = mtod(m, const struct ip *);
        struct ipflow *ipf;
        size_t hash;

        KERNEL_LOCK_UNLESS_NET_MPSAFE();
        mutex_enter(&ipflow_lock);

        /*
         * Don't create cache entries for ICMP messages.
         */
        if (ip_maxflows == 0 || ip->ip_p == IPPROTO_ICMP)
                goto out;

        /*
         * See if an existing flow struct exists.  If so remove it from its
         * list and free the old route.  If not, try to malloc a new one
         * (if we aren't at our limit).
         */
        ipf = ipflow_lookup(ip);
        if (ipf == NULL) {
                if (ipflow_inuse >= ip_maxflows) {
                        ipf = ipflow_reap(true);
                } else {
                        ipf = pool_get(&ipflow_pool, PR_NOWAIT);
                        if (ipf == NULL)
                                goto out;
                        ipflow_inuse++;
                }
                memset(ipf, 0, sizeof(*ipf));
        } else {
                IPFLOW_REMOVE(ipf->ipf_hashidx, ipf);

                ipflow_addstats(ipf);
                rtcache_free(&ipf->ipf_ro);
                ipf->ipf_uses = ipf->ipf_last_uses = 0;
                ipf->ipf_errors = ipf->ipf_dropped = 0;
        }

        /*
         * Fill in the updated information.
         */
        rtcache_copy(&ipf->ipf_ro, ro);
        ipf->ipf_dst = ip->ip_dst;
        ipf->ipf_src = ip->ip_src;
        ipf->ipf_tos = ip->ip_tos;
        PRT_SLOW_ARM(ipf->ipf_timer, IPFLOW_TIMER);

        /*
         * Insert into the appropriate bucket of the flow table.
         */
        hash = ipflow_hash(ip);
        IPFLOW_INSERT(hash, ipf);

 out:
        mutex_exit(&ipflow_lock);
        KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

int
ipflow_invalidate_all(int new_size)
{
        struct ipflow *ipf, *next_ipf;
        int error;

        error = 0;

        mutex_enter(&ipflow_lock);

        for (ipf = TAILQ_FIRST(&ipflowlist); ipf != NULL; ipf = next_ipf) {
                next_ipf = TAILQ_NEXT(ipf, ipf_list);
                ipflow_free(ipf);
        }

        if (new_size)
                error = ipflow_reinit(new_size);

        mutex_exit(&ipflow_lock);

        return error;
}

/*
 * sysctl helper routine for net.inet.ip.maxflows.
 */
static int
sysctl_net_inet_ip_maxflows(SYSCTLFN_ARGS)
{
        int error;

        error = sysctl_lookup(SYSCTLFN_CALL(rnode));
        if (error || newp == NULL)
                return (error);

        SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
        mutex_enter(&ipflow_lock);

        ipflow_reap(false);

        mutex_exit(&ipflow_lock);
        SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE();

        return (0);
}

static int
sysctl_net_inet_ip_hashsize(SYSCTLFN_ARGS)
{
        int error, tmp;
        struct sysctlnode node;

        node = *rnode;
        tmp = ip_hashsize;
        node.sysctl_data = &tmp;
        error = sysctl_lookup(SYSCTLFN_CALL(&node));
        if (error || newp == NULL)
                return (error);

        if ((tmp & (tmp - 1)) == 0 && tmp != 0) {
                /*
                 * Can only fail due to malloc()
                 */
                SOFTNET_KERNEL_LOCK_UNLESS_NET_MPSAFE();
                error = ipflow_invalidate_all(tmp);
                SOFTNET_KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
        } else {
                /*
                 * EINVAL if not a power of 2
                 */
                error = EINVAL;
        }

        return error;
}

static void
ipflow_sysctl_init(struct sysctllog **clog)
{
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "inet",
                       SYSCTL_DESCR("PF_INET related settings"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "ip",
                       SYSCTL_DESCR("IPv4 related settings"),
                       NULL, 0, NULL, 0,
                       CTL_NET, PF_INET, IPPROTO_IP, CTL_EOL);

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "maxflows",
                       SYSCTL_DESCR("Number of flows for fast forwarding"),
                       sysctl_net_inet_ip_maxflows, 0, &ip_maxflows, 0,
                       CTL_NET, PF_INET, IPPROTO_IP,
                       IPCTL_MAXFLOWS, CTL_EOL);
        sysctl_createv(clog, 0, NULL, NULL,
                        CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                        CTLTYPE_INT, "hashsize",
                        SYSCTL_DESCR("Size of hash table for fast forwarding (IPv4)"),
                        sysctl_net_inet_ip_hashsize, 0, &ip_hashsize, 0,
                        CTL_NET, PF_INET, IPPROTO_IP,
                        CTL_CREATE, CTL_EOL);
}