// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              IPv4 Forwarding Information Base: policy rules.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *              Thomas Graf <tgraf@suug.ch>
 *
 * Fixes:
 *              Rani Assaf      :       local_rule cannot be deleted
 *              Marc Boucher    :       routing by fwmark
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/netlink.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/export.h>
#include <net/flow.h>
#include <net/inet_dscp.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/ip_fib.h>
#include <net/nexthop.h>
#include <net/fib_rules.h>
#include <linux/indirect_call_wrapper.h>

struct fib4_rule {
        struct fib_rule         common;
        u8                      dst_len;
        u8                      src_len;
        dscp_t                  dscp;
        dscp_t                  dscp_mask;
        u8                      dscp_full:1;    /* DSCP or TOS selector */
        __be32                  src;
        __be32                  srcmask;
        __be32                  dst;
        __be32                  dstmask;
#ifdef CONFIG_IP_ROUTE_CLASSID
        u32                     tclassid;
#endif
};

static bool fib4_rule_matchall(const struct fib_rule *rule)
{
        struct fib4_rule *r = container_of(rule, struct fib4_rule, common);

        if (r->dst_len || r->src_len || r->dscp)
                return false;
        return fib_rule_matchall(rule);
}

bool fib4_rule_default(const struct fib_rule *rule)
{
        if (!fib4_rule_matchall(rule) || rule->action != FR_ACT_TO_TBL ||
            rule->l3mdev)
                return false;
        if (rule->table != RT_TABLE_LOCAL && rule->table != RT_TABLE_MAIN &&
            rule->table != RT_TABLE_DEFAULT)
                return false;
        return true;
}
EXPORT_SYMBOL_GPL(fib4_rule_default);

int fib4_rules_dump(struct net *net, struct notifier_block *nb,
                    struct netlink_ext_ack *extack)
{
        return fib_rules_dump(net, nb, AF_INET, extack);
}

unsigned int fib4_rules_seq_read(const struct net *net)
{
        return fib_rules_seq_read(net, AF_INET);
}

int __fib_lookup(struct net *net, struct flowi4 *flp,
                 struct fib_result *res, unsigned int flags)
{
        struct fib_lookup_arg arg = {
                .result = res,
                .flags = flags,
        };
        int err;

        /* update flow if oif or iif point to device enslaved to l3mdev */
        l3mdev_update_flow(net, flowi4_to_flowi(flp));

        err = fib_rules_lookup(net->ipv4.rules_ops, flowi4_to_flowi(flp), 0, &arg);
#ifdef CONFIG_IP_ROUTE_CLASSID
        if (arg.rule)
                res->tclassid = ((struct fib4_rule *)arg.rule)->tclassid;
        else
                res->tclassid = 0;
#endif

        if (err == -ESRCH)
                err = -ENETUNREACH;

        return err;
}
EXPORT_SYMBOL_GPL(__fib_lookup);

INDIRECT_CALLABLE_SCOPE int fib4_rule_action(struct fib_rule *rule,
                                             struct flowi *flp, int flags,
                                             struct fib_lookup_arg *arg)
{
        int err = -EAGAIN;
        struct fib_table *tbl;
        u32 tb_id;

        switch (rule->action) {
        case FR_ACT_TO_TBL:
                break;

        case FR_ACT_UNREACHABLE:
                return -ENETUNREACH;

        case FR_ACT_PROHIBIT:
                return -EACCES;

        case FR_ACT_BLACKHOLE:
        default:
                return -EINVAL;
        }

        rcu_read_lock();

        tb_id = fib_rule_get_table(rule, arg);
        tbl = fib_get_table(rule->fr_net, tb_id);
        if (tbl)
                err = fib_table_lookup(tbl, &flp->u.ip4,
                                       (struct fib_result *)arg->result,
                                       arg->flags);

        rcu_read_unlock();
        return err;
}

INDIRECT_CALLABLE_SCOPE bool fib4_rule_suppress(struct fib_rule *rule,
                                                int flags,
                                                struct fib_lookup_arg *arg)
{
        struct fib_result *result = arg->result;
        struct net_device *dev = NULL;

        if (result->fi) {
                struct fib_nh_common *nhc = fib_info_nhc(result->fi, 0);

                dev = nhc->nhc_dev;
        }

        /* do not accept result if the route does
         * not meet the required prefix length
         */
        if (result->prefixlen <= rule->suppress_prefixlen)
                goto suppress_route;

        /* do not accept result if the route uses a device
         * belonging to a forbidden interface group
         */
        if (rule->suppress_ifgroup != -1 && dev && dev->group == rule->suppress_ifgroup)
                goto suppress_route;

        return false;

suppress_route:
        if (!(arg->flags & FIB_LOOKUP_NOREF))
                fib_info_put(result->fi);
        return true;
}

INDIRECT_CALLABLE_SCOPE int fib4_rule_match(struct fib_rule *rule,
                                            struct flowi *fl, int flags)
{
        struct fib4_rule *r = (struct fib4_rule *) rule;
        struct flowi4 *fl4 = &fl->u.ip4;
        __be32 daddr = fl4->daddr;
        __be32 saddr = fl4->saddr;

        if (((saddr ^ r->src) & r->srcmask) ||
            ((daddr ^ r->dst) & r->dstmask))
                return 0;

        /* When DSCP selector is used we need to match on the entire DSCP field
         * in the flow information structure. When TOS selector is used we need
         * to mask the upper three DSCP bits prior to matching to maintain
         * legacy behavior.
         */
        if (r->dscp_full && (r->dscp ^ fl4->flowi4_dscp) & r->dscp_mask)
                return 0;
        else if (!r->dscp_full && r->dscp &&
                 !fib_dscp_masked_match(r->dscp, fl4))
                return 0;

        if (rule->ip_proto && (rule->ip_proto != fl4->flowi4_proto))
                return 0;

        if (!fib_rule_port_match(&rule->sport_range, rule->sport_mask,
                                 fl4->fl4_sport))
                return 0;

        if (!fib_rule_port_match(&rule->dport_range, rule->dport_mask,
                                 fl4->fl4_dport))
                return 0;

        return 1;
}

static struct fib_table *fib_empty_table(struct net *net)
{
        u32 id = 1;

        while (1) {
                if (!fib_get_table(net, id))
                        return fib_new_table(net, id);

                if (id++ == RT_TABLE_MAX)
                        break;
        }
        return NULL;
}

static int fib4_nl2rule_dscp(const struct nlattr *nla, struct fib4_rule *rule4,
                             struct netlink_ext_ack *extack)
{
        if (rule4->dscp) {
                NL_SET_ERR_MSG(extack, "Cannot specify both TOS and DSCP");
                return -EINVAL;
        }

        rule4->dscp = inet_dsfield_to_dscp(nla_get_u8(nla) << 2);
        rule4->dscp_mask = inet_dsfield_to_dscp(INET_DSCP_MASK);
        rule4->dscp_full = true;

        return 0;
}

static int fib4_nl2rule_dscp_mask(const struct nlattr *nla,
                                  struct fib4_rule *rule4,
                                  struct netlink_ext_ack *extack)
{
        dscp_t dscp_mask;

        if (!rule4->dscp_full) {
                NL_SET_ERR_MSG_ATTR(extack, nla,
                                    "Cannot specify DSCP mask without DSCP value");
                return -EINVAL;
        }

        dscp_mask = inet_dsfield_to_dscp(nla_get_u8(nla) << 2);
        if (rule4->dscp & ~dscp_mask) {
                NL_SET_ERR_MSG_ATTR(extack, nla, "Invalid DSCP mask");
                return -EINVAL;
        }

        rule4->dscp_mask = dscp_mask;

        return 0;
}

static int fib4_rule_configure(struct fib_rule *rule, struct sk_buff *skb,
                               struct fib_rule_hdr *frh,
                               struct nlattr **tb,
                               struct netlink_ext_ack *extack)
{
        struct fib4_rule *rule4 = (struct fib4_rule *)rule;
        struct net *net = rule->fr_net;
        int err = -EINVAL;

        if (tb[FRA_FLOWLABEL] || tb[FRA_FLOWLABEL_MASK]) {
                NL_SET_ERR_MSG(extack,
                               "Flow label cannot be specified for IPv4 FIB rules");
                goto errout;
        }

        if (!inet_validate_dscp(frh->tos)) {
                NL_SET_ERR_MSG(extack,
                               "Invalid dsfield (tos): ECN bits must be 0");
                goto errout;
        }
        /* IPv4 currently doesn't handle high order DSCP bits correctly */
        if (frh->tos & ~IPTOS_TOS_MASK) {
                NL_SET_ERR_MSG(extack, "Invalid tos");
                goto errout;
        }
        rule4->dscp = inet_dsfield_to_dscp(frh->tos);

        if (tb[FRA_DSCP] &&
            fib4_nl2rule_dscp(tb[FRA_DSCP], rule4, extack) < 0)
                goto errout;

        if (tb[FRA_DSCP_MASK] &&
            fib4_nl2rule_dscp_mask(tb[FRA_DSCP_MASK], rule4, extack) < 0)
                goto errout;

        /* split local/main if they are not already split */
        err = fib_unmerge(net);
        if (err)
                goto errout;

        if (rule->table == RT_TABLE_UNSPEC && !rule->l3mdev) {
                if (rule->action == FR_ACT_TO_TBL) {
                        struct fib_table *table;

                        table = fib_empty_table(net);
                        if (!table) {
                                err = -ENOBUFS;
                                goto errout;
                        }

                        rule->table = table->tb_id;
                }
        }

        if (frh->src_len)
                rule4->src = nla_get_in_addr(tb[FRA_SRC]);

        if (frh->dst_len)
                rule4->dst = nla_get_in_addr(tb[FRA_DST]);

#ifdef CONFIG_IP_ROUTE_CLASSID
        if (tb[FRA_FLOW]) {
                rule4->tclassid = nla_get_u32(tb[FRA_FLOW]);
                if (rule4->tclassid)
                        atomic_inc(&net->ipv4.fib_num_tclassid_users);
        }
#endif

        if (fib_rule_requires_fldissect(rule))
                net->ipv4.fib_rules_require_fldissect++;

        rule4->src_len = frh->src_len;
        rule4->srcmask = inet_make_mask(rule4->src_len);
        rule4->dst_len = frh->dst_len;
        rule4->dstmask = inet_make_mask(rule4->dst_len);

        net->ipv4.fib_has_custom_rules = true;

        err = 0;
errout:
        return err;
}

static int fib4_rule_delete(struct fib_rule *rule)
{
        struct net *net = rule->fr_net;
        int err;

        /* split local/main if they are not already split */
        err = fib_unmerge(net);
        if (err)
                goto errout;

#ifdef CONFIG_IP_ROUTE_CLASSID
        if (((struct fib4_rule *)rule)->tclassid)
                atomic_dec(&net->ipv4.fib_num_tclassid_users);
#endif
        net->ipv4.fib_has_custom_rules = true;

        if (net->ipv4.fib_rules_require_fldissect &&
            fib_rule_requires_fldissect(rule))
                net->ipv4.fib_rules_require_fldissect--;
errout:
        return err;
}

static int fib4_rule_compare(struct fib_rule *rule, struct fib_rule_hdr *frh,
                             struct nlattr **tb)
{
        struct fib4_rule *rule4 = (struct fib4_rule *) rule;

        if (frh->src_len && (rule4->src_len != frh->src_len))
                return 0;

        if (frh->dst_len && (rule4->dst_len != frh->dst_len))
                return 0;

        if (frh->tos &&
            (rule4->dscp_full ||
             inet_dscp_to_dsfield(rule4->dscp) != frh->tos))
                return 0;

        if (tb[FRA_DSCP]) {
                dscp_t dscp;

                dscp = inet_dsfield_to_dscp(nla_get_u8(tb[FRA_DSCP]) << 2);
                if (!rule4->dscp_full || rule4->dscp != dscp)
                        return 0;
        }

        if (tb[FRA_DSCP_MASK]) {
                dscp_t dscp_mask;

                dscp_mask = inet_dsfield_to_dscp(nla_get_u8(tb[FRA_DSCP_MASK]) << 2);
                if (!rule4->dscp_full || rule4->dscp_mask != dscp_mask)
                        return 0;
        }

#ifdef CONFIG_IP_ROUTE_CLASSID
        if (tb[FRA_FLOW] && (rule4->tclassid != nla_get_u32(tb[FRA_FLOW])))
                return 0;
#endif

        if (frh->src_len && (rule4->src != nla_get_in_addr(tb[FRA_SRC])))
                return 0;

        if (frh->dst_len && (rule4->dst != nla_get_in_addr(tb[FRA_DST])))
                return 0;

        return 1;
}

static int fib4_rule_fill(struct fib_rule *rule, struct sk_buff *skb,
                          struct fib_rule_hdr *frh)
{
        struct fib4_rule *rule4 = (struct fib4_rule *) rule;

        frh->dst_len = rule4->dst_len;
        frh->src_len = rule4->src_len;

        if (rule4->dscp_full) {
                frh->tos = 0;
                if (nla_put_u8(skb, FRA_DSCP,
                               inet_dscp_to_dsfield(rule4->dscp) >> 2) ||
                    nla_put_u8(skb, FRA_DSCP_MASK,
                               inet_dscp_to_dsfield(rule4->dscp_mask) >> 2))
                        goto nla_put_failure;
        } else {
                frh->tos = inet_dscp_to_dsfield(rule4->dscp);
        }

        if ((rule4->dst_len &&
             nla_put_in_addr(skb, FRA_DST, rule4->dst)) ||
            (rule4->src_len &&
             nla_put_in_addr(skb, FRA_SRC, rule4->src)))
                goto nla_put_failure;
#ifdef CONFIG_IP_ROUTE_CLASSID
        if (rule4->tclassid &&
            nla_put_u32(skb, FRA_FLOW, rule4->tclassid))
                goto nla_put_failure;
#endif
        return 0;

nla_put_failure:
        return -ENOBUFS;
}

static size_t fib4_rule_nlmsg_payload(struct fib_rule *rule)
{
        return nla_total_size(4) /* dst */
               + nla_total_size(4) /* src */
               + nla_total_size(4) /* flow */
               + nla_total_size(1) /* dscp */
               + nla_total_size(1); /* dscp mask */
}

static void fib4_rule_flush_cache(struct fib_rules_ops *ops)
{
        rt_cache_flush(ops->fro_net);
}

static const struct fib_rules_ops __net_initconst fib4_rules_ops_template = {
        .family         = AF_INET,
        .rule_size      = sizeof(struct fib4_rule),
        .addr_size      = sizeof(u32),
        .action         = fib4_rule_action,
        .suppress       = fib4_rule_suppress,
        .match          = fib4_rule_match,
        .configure      = fib4_rule_configure,
        .delete         = fib4_rule_delete,
        .compare        = fib4_rule_compare,
        .fill           = fib4_rule_fill,
        .nlmsg_payload  = fib4_rule_nlmsg_payload,
        .flush_cache    = fib4_rule_flush_cache,
        .nlgroup        = RTNLGRP_IPV4_RULE,
        .owner          = THIS_MODULE,
};

static int fib_default_rules_init(struct fib_rules_ops *ops)
{
        int err;

        err = fib_default_rule_add(ops, 0, RT_TABLE_LOCAL);
        if (err < 0)
                return err;
        err = fib_default_rule_add(ops, 0x7FFE, RT_TABLE_MAIN);
        if (err < 0)
                return err;
        err = fib_default_rule_add(ops, 0x7FFF, RT_TABLE_DEFAULT);
        if (err < 0)
                return err;
        return 0;
}

int __net_init fib4_rules_init(struct net *net)
{
        int err;
        struct fib_rules_ops *ops;

        ops = fib_rules_register(&fib4_rules_ops_template, net);
        if (IS_ERR(ops))
                return PTR_ERR(ops);

        err = fib_default_rules_init(ops);
        if (err < 0)
                goto fail;
        net->ipv4.rules_ops = ops;
        net->ipv4.fib_has_custom_rules = false;
        net->ipv4.fib_rules_require_fldissect = 0;
        return 0;

fail:
        /* also cleans all rules already added */
        fib_rules_unregister(ops);
        return err;
}

void __net_exit fib4_rules_exit(struct net *net)
{
        fib_rules_unregister(net->ipv4.rules_ops);
}