/*
 * Geneve: Generic Network Virtualization Encapsulation
 *
 * Copyright (c) 2014 Nicira, Inc.
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/skbuff.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/igmp.h>
#include <linux/etherdevice.h>
#include <linux/if_ether.h>
#include <linux/if_vlan.h>
#include <linux/ethtool.h>
#include <linux/mutex.h>
#include <net/arp.h>
#include <net/ndisc.h>
#include <net/ip.h>
#include <net/ip_tunnels.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/rtnetlink.h>
#include <net/route.h>
#include <net/dsfield.h>
#include <net/inet_ecn.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/geneve.h>
#include <net/protocol.h>
#include <net/udp_tunnel.h>
#if IS_ENABLED(CONFIG_IPV6)
#include <net/ipv6.h>
#include <net/addrconf.h>
#include <net/ip6_tunnel.h>
#include <net/ip6_checksum.h>
#endif

/* Protects sock_list and refcounts. */
static DEFINE_MUTEX(geneve_mutex);

/* per-network namespace private data for this module */
struct geneve_net {
	struct list_head	sock_list;
};

static int geneve_net_id;

static inline struct genevehdr *geneve_hdr(const struct sk_buff *skb)
{
	return (struct genevehdr *)(udp_hdr(skb) + 1);
}

static struct geneve_sock *geneve_find_sock(struct net *net,
					    sa_family_t family, __be16 port)
{
	struct geneve_net *gn = net_generic(net, geneve_net_id);
	struct geneve_sock *gs;

	list_for_each_entry(gs, &gn->sock_list, list) {
		if (inet_sk(gs->sock->sk)->inet_sport == port &&
		    inet_sk(gs->sock->sk)->sk.sk_family == family)
			return gs;
	}

	return NULL;
}

static void geneve_build_header(struct genevehdr *geneveh,
				__be16 tun_flags, u8 vni[3],
				u8 options_len, u8 *options)
{
	geneveh->ver = GENEVE_VER;
	geneveh->opt_len = options_len / 4;
	geneveh->oam = !!(tun_flags & TUNNEL_OAM);
	geneveh->critical = !!(tun_flags & TUNNEL_CRIT_OPT);
	geneveh->rsvd1 = 0;
	memcpy(geneveh->vni, vni, 3);
	geneveh->proto_type = htons(ETH_P_TEB);
	geneveh->rsvd2 = 0;

	memcpy(geneveh->options, options, options_len);
}

/* Transmit a fully formatted Geneve frame.
 *
 * When calling this function. The skb->data should point
 * to the geneve header which is fully formed.
 *
 * This function will add other UDP tunnel headers.
 */
int geneve_xmit_skb(struct geneve_sock *gs, struct rtable *rt,
		    struct sk_buff *skb, __be32 src, __be32 dst, __u8 tos,
		    __u8 ttl, __be16 df, __be16 src_port, __be16 dst_port,
		    __be16 tun_flags, u8 vni[3], u8 opt_len, u8 *opt,
		    bool csum, bool xnet)
{
	struct genevehdr *gnvh;
	int min_headroom;
	int err;

	min_headroom = LL_RESERVED_SPACE(rt->dst.dev) + rt->dst.header_len
			+ GENEVE_BASE_HLEN + opt_len + sizeof(struct iphdr)
			+ (skb_vlan_tag_present(skb) ? VLAN_HLEN : 0);

	err = skb_cow_head(skb, min_headroom);
	if (unlikely(err)) {
		kfree_skb(skb);
		return err;
	}

	skb = vlan_hwaccel_push_inside(skb);
	if (unlikely(!skb))
		return -ENOMEM;

	skb = udp_tunnel_handle_offloads(skb, csum);
	if (IS_ERR(skb))
		return PTR_ERR(skb);

	gnvh = (struct genevehdr *)__skb_push(skb, sizeof(*gnvh) + opt_len);
	geneve_build_header(gnvh, tun_flags, vni, opt_len, opt);

	skb_set_inner_protocol(skb, htons(ETH_P_TEB));

	return udp_tunnel_xmit_skb(rt, gs->sock->sk, skb, src, dst,
				   tos, ttl, df, src_port, dst_port, xnet,
				   !csum);
}
EXPORT_SYMBOL_GPL(geneve_xmit_skb);

static int geneve_hlen(struct genevehdr *gh)
{
	return sizeof(*gh) + gh->opt_len * 4;
}

static struct sk_buff **geneve_gro_receive(struct sk_buff **head,
					   struct sk_buff *skb,
					   struct udp_offload *uoff)
{
	struct sk_buff *p, **pp = NULL;
	struct genevehdr *gh, *gh2;
	unsigned int hlen, gh_len, off_gnv;
	const struct packet_offload *ptype;
	__be16 type;
	int flush = 1;

	off_gnv = skb_gro_offset(skb);
	hlen = off_gnv + sizeof(*gh);
	gh = skb_gro_header_fast(skb, off_gnv);
	if (skb_gro_header_hard(skb, hlen)) {
		gh = skb_gro_header_slow(skb, hlen, off_gnv);
		if (unlikely(!gh))
			goto out;
	}

	if (gh->ver != GENEVE_VER || gh->oam)
		goto out;
	gh_len = geneve_hlen(gh);

	hlen = off_gnv + gh_len;
	if (skb_gro_header_hard(skb, hlen)) {
		gh = skb_gro_header_slow(skb, hlen, off_gnv);
		if (unlikely(!gh))
			goto out;
	}

	flush = 0;

	for (p = *head; p; p = p->next) {
		if (!NAPI_GRO_CB(p)->same_flow)
			continue;

		gh2 = (struct genevehdr *)(p->data + off_gnv);
		if (gh->opt_len != gh2->opt_len ||
		    memcmp(gh, gh2, gh_len)) {
			NAPI_GRO_CB(p)->same_flow = 0;
			continue;
		}
	}

	type = gh->proto_type;

	rcu_read_lock();
	ptype = gro_find_receive_by_type(type);
	if (!ptype) {
		flush = 1;
		goto out_unlock;
	}

	skb_gro_pull(skb, gh_len);
	skb_gro_postpull_rcsum(skb, gh, gh_len);
	pp = ptype->callbacks.gro_receive(head, skb);

out_unlock:
	rcu_read_unlock();
out:
	NAPI_GRO_CB(skb)->flush |= flush;

	return pp;
}

static int geneve_gro_complete(struct sk_buff *skb, int nhoff,
			       struct udp_offload *uoff)
{
	struct genevehdr *gh;
	struct packet_offload *ptype;
	__be16 type;
	int gh_len;
	int err = -ENOSYS;

	udp_tunnel_gro_complete(skb, nhoff);

	gh = (struct genevehdr *)(skb->data + nhoff);
	gh_len = geneve_hlen(gh);
	type = gh->proto_type;

	rcu_read_lock();
	ptype = gro_find_complete_by_type(type);
	if (ptype)
		err = ptype->callbacks.gro_complete(skb, nhoff + gh_len);

	rcu_read_unlock();
	return err;
}

static void geneve_notify_add_rx_port(struct geneve_sock *gs)
{
	struct sock *sk = gs->sock->sk;
	sa_family_t sa_family = sk->sk_family;
	int err;

	if (sa_family == AF_INET) {
		err = udp_add_offload(&gs->udp_offloads);
		if (err)
			pr_warn("geneve: udp_add_offload failed with status %d\n",
				err);
	}
}

static void geneve_notify_del_rx_port(struct geneve_sock *gs)
{
	struct sock *sk = gs->sock->sk;
	sa_family_t sa_family = sk->sk_family;

	if (sa_family == AF_INET)
		udp_del_offload(&gs->udp_offloads);
}

/* Callback from net/ipv4/udp.c to receive packets */
static int geneve_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
{
	struct genevehdr *geneveh;
	struct geneve_sock *gs;
	int opts_len;

	/* Need Geneve and inner Ethernet header to be present */
	if (unlikely(!pskb_may_pull(skb, GENEVE_BASE_HLEN)))
		goto error;

	/* Return packets with reserved bits set */
	geneveh = geneve_hdr(skb);

	if (unlikely(geneveh->ver != GENEVE_VER))
		goto error;

	if (unlikely(geneveh->proto_type != htons(ETH_P_TEB)))
		goto error;

	opts_len = geneveh->opt_len * 4;
	if (iptunnel_pull_header(skb, GENEVE_BASE_HLEN + opts_len,
				 htons(ETH_P_TEB)))
		goto drop;

	gs = rcu_dereference_sk_user_data(sk);
	if (!gs)
		goto drop;

	gs->rcv(gs, skb);
	return 0;

drop:
	/* Consume bad packet */
	kfree_skb(skb);
	return 0;

error:
	/* Let the UDP layer deal with the skb */
	return 1;
}

static struct socket *geneve_create_sock(struct net *net, bool ipv6,
					 __be16 port)
{
	struct socket *sock;
	struct udp_port_cfg udp_conf;
	int err;

	memset(&udp_conf, 0, sizeof(udp_conf));

	if (ipv6) {
		udp_conf.family = AF_INET6;
	} else {
		udp_conf.family = AF_INET;
		udp_conf.local_ip.s_addr = htonl(INADDR_ANY);
	}

	udp_conf.local_udp_port = port;

	/* Open UDP socket */
	err = udp_sock_create(net, &udp_conf, &sock);
	if (err < 0)
		return ERR_PTR(err);

	return sock;
}

/* Create new listen socket if needed */
static struct geneve_sock *geneve_socket_create(struct net *net, __be16 port,
						geneve_rcv_t *rcv, void *data,
						bool ipv6)
{
	struct geneve_net *gn = net_generic(net, geneve_net_id);
	struct geneve_sock *gs;
	struct socket *sock;
	struct udp_tunnel_sock_cfg tunnel_cfg;

	gs = kzalloc(sizeof(*gs), GFP_KERNEL);
	if (!gs)
		return ERR_PTR(-ENOMEM);

	sock = geneve_create_sock(net, ipv6, port);
	if (IS_ERR(sock)) {
		kfree(gs);
		return ERR_CAST(sock);
	}

	gs->sock = sock;
	gs->refcnt = 1;
	gs->rcv = rcv;
	gs->rcv_data = data;

	/* Initialize the geneve udp offloads structure */
	gs->udp_offloads.port = port;
	gs->udp_offloads.callbacks.gro_receive  = geneve_gro_receive;
	gs->udp_offloads.callbacks.gro_complete = geneve_gro_complete;
	geneve_notify_add_rx_port(gs);

	/* Mark socket as an encapsulation socket */
	tunnel_cfg.sk_user_data = gs;
	tunnel_cfg.encap_type = 1;
	tunnel_cfg.encap_rcv = geneve_udp_encap_recv;
	tunnel_cfg.encap_destroy = NULL;
	setup_udp_tunnel_sock(net, sock, &tunnel_cfg);

	list_add(&gs->list, &gn->sock_list);

	return gs;
}

struct geneve_sock *geneve_sock_add(struct net *net, __be16 port,
				    geneve_rcv_t *rcv, void *data,
				    bool no_share, bool ipv6)
{
	struct geneve_sock *gs;

	mutex_lock(&geneve_mutex);

	gs = geneve_find_sock(net, ipv6 ? AF_INET6 : AF_INET, port);
	if (gs) {
		if (!no_share && gs->rcv == rcv)
			gs->refcnt++;
		else
			gs = ERR_PTR(-EBUSY);
	} else {
		gs = geneve_socket_create(net, port, rcv, data, ipv6);
	}

	mutex_unlock(&geneve_mutex);

	return gs;
}
EXPORT_SYMBOL_GPL(geneve_sock_add);

void geneve_sock_release(struct geneve_sock *gs)
{
	mutex_lock(&geneve_mutex);

	if (--gs->refcnt)
		goto unlock;

	list_del(&gs->list);
	geneve_notify_del_rx_port(gs);
	udp_tunnel_sock_release(gs->sock);
	kfree_rcu(gs, rcu);

unlock:
	mutex_unlock(&geneve_mutex);
}
EXPORT_SYMBOL_GPL(geneve_sock_release);

static __net_init int geneve_init_net(struct net *net)
{
	struct geneve_net *gn = net_generic(net, geneve_net_id);

	INIT_LIST_HEAD(&gn->sock_list);

	return 0;
}

static struct pernet_operations geneve_net_ops = {
	.init = geneve_init_net,
	.id   = &geneve_net_id,
	.size = sizeof(struct geneve_net),
};

static int __init geneve_init_module(void)
{
	int rc;

	rc = register_pernet_subsys(&geneve_net_ops);
	if (rc)
		return rc;

	pr_info("Geneve driver\n");

	return 0;
}
module_init(geneve_init_module);

static void __exit geneve_cleanup_module(void)
{
	unregister_pernet_subsys(&geneve_net_ops);
}
module_exit(geneve_cleanup_module);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jesse Gross <jesse@nicira.com>");
MODULE_DESCRIPTION("Driver for GENEVE encapsulated traffic");