// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ip_vs_proto_udp.c:   UDP load balancing support for IPVS
 *
 * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
 *              Julian Anastasov <ja@ssi.bg>
 *
 * Changes:     Hans Schillstrom <hans.schillstrom@ericsson.com>
 *              Network name space (netns) aware.
 */

#define pr_fmt(fmt) "IPVS: " fmt

#include <linux/in.h>
#include <linux/ip.h>
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/udp.h>
#include <linux/indirect_call_wrapper.h>

#include <net/ip_vs.h>
#include <net/ip.h>
#include <net/ip6_checksum.h>

static int
udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
               unsigned int udphoff);

static int
udp_conn_schedule(struct netns_ipvs *ipvs, int af, struct sk_buff *skb,
                  struct ip_vs_proto_data *pd,
                  int *verdict, struct ip_vs_conn **cpp,
                  struct ip_vs_iphdr *iph)
{
        struct ip_vs_service *svc;
        struct udphdr _udph, *uh;
        __be16 _ports[2], *ports = NULL;

        if (likely(!ip_vs_iph_icmp(iph))) {
                /* IPv6 fragments, only first fragment will hit this */
                uh = skb_header_pointer(skb, iph->len, sizeof(_udph), &_udph);
                if (uh)
                        ports = &uh->source;
        } else {
                ports = skb_header_pointer(
                        skb, iph->len, sizeof(_ports), &_ports);
        }

        if (!ports) {
                *verdict = NF_DROP;
                return 0;
        }

        if (likely(!ip_vs_iph_inverse(iph)))
                svc = ip_vs_service_find(ipvs, af, skb->mark, iph->protocol,
                                         &iph->daddr, ports[1]);
        else
                svc = ip_vs_service_find(ipvs, af, skb->mark, iph->protocol,
                                         &iph->saddr, ports[0]);

        if (svc) {
                int ignored;

                if (ip_vs_todrop(ipvs)) {
                        /*
                         * It seems that we are very loaded.
                         * We have to drop this packet :(
                         */
                        *verdict = NF_DROP;
                        return 0;
                }

                /*
                 * Let the virtual server select a real server for the
                 * incoming connection, and create a connection entry.
                 */
                *cpp = ip_vs_schedule(svc, skb, pd, &ignored, iph);
                if (!*cpp && ignored <= 0) {
                        if (!ignored)
                                *verdict = ip_vs_leave(svc, skb, pd, iph);
                        else
                                *verdict = NF_DROP;
                        return 0;
                }
        }
        /* NF_ACCEPT */
        return 1;
}


static inline void
udp_fast_csum_update(int af, struct udphdr *uhdr,
                     const union nf_inet_addr *oldip,
                     const union nf_inet_addr *newip,
                     __be16 oldport, __be16 newport)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                uhdr->check =
                        csum_fold(ip_vs_check_diff16(oldip->ip6, newip->ip6,
                                         ip_vs_check_diff2(oldport, newport,
                                                ~csum_unfold(uhdr->check))));
        else
#endif
                uhdr->check =
                        csum_fold(ip_vs_check_diff4(oldip->ip, newip->ip,
                                         ip_vs_check_diff2(oldport, newport,
                                                ~csum_unfold(uhdr->check))));
        if (!uhdr->check)
                uhdr->check = CSUM_MANGLED_0;
}

static inline void
udp_partial_csum_update(int af, struct udphdr *uhdr,
                     const union nf_inet_addr *oldip,
                     const union nf_inet_addr *newip,
                     __be16 oldlen, __be16 newlen)
{
#ifdef CONFIG_IP_VS_IPV6
        if (af == AF_INET6)
                uhdr->check =
                        ~csum_fold(ip_vs_check_diff16(oldip->ip6, newip->ip6,
                                         ip_vs_check_diff2(oldlen, newlen,
                                                csum_unfold(uhdr->check))));
        else
#endif
        uhdr->check =
                ~csum_fold(ip_vs_check_diff4(oldip->ip, newip->ip,
                                ip_vs_check_diff2(oldlen, newlen,
                                                csum_unfold(uhdr->check))));
}


INDIRECT_CALLABLE_SCOPE int
udp_snat_handler(struct sk_buff *skb, struct ip_vs_protocol *pp,
                 struct ip_vs_conn *cp, struct ip_vs_iphdr *iph)
{
        struct udphdr *udph;
        unsigned int udphoff = iph->len;
        bool payload_csum = false;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6 && iph->fragoffs)
                return 1;
#endif
        oldlen = skb->len - udphoff;

        /* csum_check requires unshared skb */
        if (skb_ensure_writable(skb, udphoff + sizeof(*udph)))
                return 0;

        if (unlikely(cp->app != NULL)) {
                int ret;

                /* Some checks before mangling */
                if (!udp_csum_check(cp->af, skb, pp, udphoff))
                        return 0;

                /*
                 *      Call application helper if needed
                 */
                if (!(ret = ip_vs_app_pkt_out(cp, skb, iph)))
                        return 0;
                /* ret=2: csum update is needed after payload mangling */
                if (ret == 1)
                        oldlen = skb->len - udphoff;
                else
                        payload_csum = true;
        }

        udph = (void *)skb_network_header(skb) + udphoff;
        udph->source = cp->vport;

        /*
         *      Adjust UDP checksums
         */
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                udp_partial_csum_update(cp->af, udph, &cp->daddr, &cp->vaddr,
                                        htons(oldlen),
                                        htons(skb->len - udphoff));
        } else if (!payload_csum && (udph->check != 0)) {
                /* Only port and addr are changed, do fast csum update */
                udp_fast_csum_update(cp->af, udph, &cp->daddr, &cp->vaddr,
                                     cp->dport, cp->vport);
                if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = cp->app ?
                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
        } else {
                /* full checksum calculation */
                udph->check = 0;
                skb->csum = skb_checksum(skb, udphoff, skb->len - udphoff, 0);
#ifdef CONFIG_IP_VS_IPV6
                if (cp->af == AF_INET6)
                        udph->check = csum_ipv6_magic(&cp->vaddr.in6,
                                                      &cp->caddr.in6,
                                                      skb->len - udphoff,
                                                      cp->protocol, skb->csum);
                else
#endif
                        udph->check = csum_tcpudp_magic(cp->vaddr.ip,
                                                        cp->caddr.ip,
                                                        skb->len - udphoff,
                                                        cp->protocol,
                                                        skb->csum);
                if (udph->check == 0)
                        udph->check = CSUM_MANGLED_0;
                skb->ip_summed = CHECKSUM_UNNECESSARY;
                IP_VS_DBG(11, "O-pkt: %s O-csum=%d (+%zd)\n",
                          pp->name, udph->check,
                          (char*)&(udph->check) - (char*)udph);
        }
        return 1;
}


static int
udp_dnat_handler(struct sk_buff *skb, struct ip_vs_protocol *pp,
                 struct ip_vs_conn *cp, struct ip_vs_iphdr *iph)
{
        struct udphdr *udph;
        unsigned int udphoff = iph->len;
        bool payload_csum = false;
        int oldlen;

#ifdef CONFIG_IP_VS_IPV6
        if (cp->af == AF_INET6 && iph->fragoffs)
                return 1;
#endif
        oldlen = skb->len - udphoff;

        /* csum_check requires unshared skb */
        if (skb_ensure_writable(skb, udphoff + sizeof(*udph)))
                return 0;

        if (unlikely(cp->app != NULL)) {
                int ret;

                /* Some checks before mangling */
                if (!udp_csum_check(cp->af, skb, pp, udphoff))
                        return 0;

                /*
                 *      Attempt ip_vs_app call.
                 *      It will fix ip_vs_conn
                 */
                if (!(ret = ip_vs_app_pkt_in(cp, skb, iph)))
                        return 0;
                /* ret=2: csum update is needed after payload mangling */
                if (ret == 1)
                        oldlen = skb->len - udphoff;
                else
                        payload_csum = true;
        }

        udph = (void *)skb_network_header(skb) + udphoff;
        udph->dest = cp->dport;

        /*
         *      Adjust UDP checksums
         */
        if (skb->ip_summed == CHECKSUM_PARTIAL) {
                udp_partial_csum_update(cp->af, udph, &cp->vaddr, &cp->daddr,
                                        htons(oldlen),
                                        htons(skb->len - udphoff));
        } else if (!payload_csum && (udph->check != 0)) {
                /* Only port and addr are changed, do fast csum update */
                udp_fast_csum_update(cp->af, udph, &cp->vaddr, &cp->daddr,
                                     cp->vport, cp->dport);
                if (skb->ip_summed == CHECKSUM_COMPLETE)
                        skb->ip_summed = cp->app ?
                                         CHECKSUM_UNNECESSARY : CHECKSUM_NONE;
        } else {
                /* full checksum calculation */
                udph->check = 0;
                skb->csum = skb_checksum(skb, udphoff, skb->len - udphoff, 0);
#ifdef CONFIG_IP_VS_IPV6
                if (cp->af == AF_INET6)
                        udph->check = csum_ipv6_magic(&cp->caddr.in6,
                                                      &cp->daddr.in6,
                                                      skb->len - udphoff,
                                                      cp->protocol, skb->csum);
                else
#endif
                        udph->check = csum_tcpudp_magic(cp->caddr.ip,
                                                        cp->daddr.ip,
                                                        skb->len - udphoff,
                                                        cp->protocol,
                                                        skb->csum);
                if (udph->check == 0)
                        udph->check = CSUM_MANGLED_0;
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        }
        return 1;
}


static int
udp_csum_check(int af, struct sk_buff *skb, struct ip_vs_protocol *pp,
               unsigned int udphoff)
{
        struct udphdr _udph, *uh;

        uh = skb_header_pointer(skb, udphoff, sizeof(_udph), &_udph);
        if (uh == NULL)
                return 0;

        if (uh->check != 0) {
                switch (skb->ip_summed) {
                case CHECKSUM_NONE:
                        skb->csum = skb_checksum(skb, udphoff,
                                                 skb->len - udphoff, 0);
                        fallthrough;
                case CHECKSUM_COMPLETE:
#ifdef CONFIG_IP_VS_IPV6
                        if (af == AF_INET6) {
                                if (csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
                                                    &ipv6_hdr(skb)->daddr,
                                                    skb->len - udphoff,
                                                    IPPROTO_UDP,
                                                    skb->csum)) {
                                        IP_VS_DBG_RL_PKT(0, af, pp, skb, 0,
                                                         "Failed checksum for");
                                        return 0;
                                }
                        } else
#endif
                                if (csum_tcpudp_magic(ip_hdr(skb)->saddr,
                                                      ip_hdr(skb)->daddr,
                                                      skb->len - udphoff,
                                                      ip_hdr(skb)->protocol,
                                                      skb->csum)) {
                                        IP_VS_DBG_RL_PKT(0, af, pp, skb, 0,
                                                         "Failed checksum for");
                                        return 0;
                                }
                        break;
                default:
                        /* No need to checksum. */
                        break;
                }
        }
        return 1;
}

static inline __u16 udp_app_hashkey(__be16 port)
{
        return (((__force u16)port >> UDP_APP_TAB_BITS) ^ (__force u16)port)
                & UDP_APP_TAB_MASK;
}


static int udp_register_app(struct netns_ipvs *ipvs, struct ip_vs_app *inc)
{
        struct ip_vs_app *i;
        __u16 hash;
        __be16 port = inc->port;
        int ret = 0;
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(ipvs, IPPROTO_UDP);

        hash = udp_app_hashkey(port);

        list_for_each_entry(i, &ipvs->udp_apps[hash], p_list) {
                if (i->port == port) {
                        ret = -EEXIST;
                        goto out;
                }
        }
        list_add_rcu(&inc->p_list, &ipvs->udp_apps[hash]);
        atomic_inc(&pd->appcnt);

  out:
        return ret;
}


static void
udp_unregister_app(struct netns_ipvs *ipvs, struct ip_vs_app *inc)
{
        struct ip_vs_proto_data *pd = ip_vs_proto_data_get(ipvs, IPPROTO_UDP);

        atomic_dec(&pd->appcnt);
        list_del_rcu(&inc->p_list);
}


static int udp_app_conn_bind(struct ip_vs_conn *cp)
{
        struct netns_ipvs *ipvs = cp->ipvs;
        int hash;
        struct ip_vs_app *inc;
        int result = 0;

        /* Default binding: bind app only for NAT */
        if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ)
                return 0;

        /* Lookup application incarnations and bind the right one */
        hash = udp_app_hashkey(cp->vport);

        list_for_each_entry_rcu(inc, &ipvs->udp_apps[hash], p_list) {
                if (inc->port == cp->vport) {
                        if (unlikely(!ip_vs_app_inc_get(inc)))
                                break;

                        IP_VS_DBG_BUF(9, "%s(): Binding conn %s:%u->"
                                      "%s:%u to app %s on port %u\n",
                                      __func__,
                                      IP_VS_DBG_ADDR(cp->af, &cp->caddr),
                                      ntohs(cp->cport),
                                      IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
                                      ntohs(cp->vport),
                                      inc->name, ntohs(inc->port));

                        cp->app = inc;
                        if (inc->init_conn)
                                result = inc->init_conn(inc, cp);
                        break;
                }
        }

        return result;
}


static const int udp_timeouts[IP_VS_UDP_S_LAST+1] = {
        [IP_VS_UDP_S_NORMAL]            =       5*60*HZ,
        [IP_VS_UDP_S_LAST]              =       2*HZ,
};

static const char *const udp_state_name_table[IP_VS_UDP_S_LAST+1] = {
        [IP_VS_UDP_S_NORMAL]            =       "UDP",
        [IP_VS_UDP_S_LAST]              =       "BUG!",
};

static const char * udp_state_name(int state)
{
        if (state >= IP_VS_UDP_S_LAST)
                return "ERR!";
        return udp_state_name_table[state] ? udp_state_name_table[state] : "?";
}

static void
udp_state_transition(struct ip_vs_conn *cp, int direction,
                     const struct sk_buff *skb,
                     struct ip_vs_proto_data *pd)
{
        if (unlikely(!pd)) {
                pr_err("UDP no ns data\n");
                return;
        }

        cp->timeout = pd->timeout_table[IP_VS_UDP_S_NORMAL];
        if (direction == IP_VS_DIR_OUTPUT)
                ip_vs_control_assure_ct(cp);
}

static int __udp_init(struct netns_ipvs *ipvs, struct ip_vs_proto_data *pd)
{
        ip_vs_init_hash_table(ipvs->udp_apps, UDP_APP_TAB_SIZE);
        pd->timeout_table = ip_vs_create_timeout_table((int *)udp_timeouts,
                                                        sizeof(udp_timeouts));
        if (!pd->timeout_table)
                return -ENOMEM;
        return 0;
}

static void __udp_exit(struct netns_ipvs *ipvs, struct ip_vs_proto_data *pd)
{
        kfree(pd->timeout_table);
}


struct ip_vs_protocol ip_vs_protocol_udp = {
        .name =                 "UDP",
        .protocol =             IPPROTO_UDP,
        .num_states =           IP_VS_UDP_S_LAST,
        .dont_defrag =          0,
        .init =                 NULL,
        .exit =                 NULL,
        .init_netns =           __udp_init,
        .exit_netns =           __udp_exit,
        .conn_schedule =        udp_conn_schedule,
        .conn_in_get =          ip_vs_conn_in_get_proto,
        .conn_out_get =         ip_vs_conn_out_get_proto,
        .snat_handler =         udp_snat_handler,
        .dnat_handler =         udp_dnat_handler,
        .state_transition =     udp_state_transition,
        .state_name =           udp_state_name,
        .register_app =         udp_register_app,
        .unregister_app =       udp_unregister_app,
        .app_conn_bind =        udp_app_conn_bind,
        .debug_packet =         ip_vs_tcpudp_debug_packet,
        .timeout_change =       NULL,
};