// SPDX-License-Identifier: GPL-2.0
/*
 * Management Component Transport Protocol (MCTP)
 *
 * Copyright (c) 2021 Code Construct
 * Copyright (c) 2021 Google
 */

#include <linux/if_arp.h>
#include <linux/net.h>
#include <linux/mctp.h>
#include <linux/module.h>
#include <linux/socket.h>

#include <net/mctp.h>
#include <net/mctpdevice.h>
#include <net/sock.h>

/* socket implementation */

static int mctp_release(struct socket *sock)
{
	struct sock *sk = sock->sk;

	if (sk) {
		sock->sk = NULL;
		sk->sk_prot->close(sk, 0);
	}

	return 0;
}

/* Generic sockaddr checks, padding checks only so far */
static bool mctp_sockaddr_is_ok(const struct sockaddr_mctp *addr)
{
	return !addr->__smctp_pad0 && !addr->__smctp_pad1;
}

static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
{
	struct sock *sk = sock->sk;
	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
	struct sockaddr_mctp *smctp;
	int rc;

	if (addrlen < sizeof(*smctp))
		return -EINVAL;

	if (addr->sa_family != AF_MCTP)
		return -EAFNOSUPPORT;

	if (!capable(CAP_NET_BIND_SERVICE))
		return -EACCES;

	/* it's a valid sockaddr for MCTP, cast and do protocol checks */
	smctp = (struct sockaddr_mctp *)addr;

	if (!mctp_sockaddr_is_ok(smctp))
		return -EINVAL;

	lock_sock(sk);

	if (sk_hashed(sk)) {
		rc = -EADDRINUSE;
		goto out_release;
	}
	msk->bind_net = smctp->smctp_network;
	msk->bind_addr = smctp->smctp_addr.s_addr;
	msk->bind_type = smctp->smctp_type & 0x7f; /* ignore the IC bit */

	rc = sk->sk_prot->hash(sk);

out_release:
	release_sock(sk);

	return rc;
}

static int mctp_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
{
	DECLARE_SOCKADDR(struct sockaddr_mctp *, addr, msg->msg_name);
	const int hlen = MCTP_HEADER_MAXLEN + sizeof(struct mctp_hdr);
	int rc, addrlen = msg->msg_namelen;
	struct sock *sk = sock->sk;
	struct mctp_skb_cb *cb;
	struct mctp_route *rt;
	struct sk_buff *skb;

	if (addr) {
		if (addrlen < sizeof(struct sockaddr_mctp))
			return -EINVAL;
		if (addr->smctp_family != AF_MCTP)
			return -EINVAL;
		if (!mctp_sockaddr_is_ok(addr))
			return -EINVAL;
		if (addr->smctp_tag & ~(MCTP_TAG_MASK | MCTP_TAG_OWNER))
			return -EINVAL;

	} else {
		/* TODO: connect()ed sockets */
		return -EDESTADDRREQ;
	}

	if (!capable(CAP_NET_RAW))
		return -EACCES;

	if (addr->smctp_network == MCTP_NET_ANY)
		addr->smctp_network = mctp_default_net(sock_net(sk));

	rt = mctp_route_lookup(sock_net(sk), addr->smctp_network,
			       addr->smctp_addr.s_addr);
	if (!rt)
		return -EHOSTUNREACH;

	skb = sock_alloc_send_skb(sk, hlen + 1 + len,
				  msg->msg_flags & MSG_DONTWAIT, &rc);
	if (!skb)
		return rc;

	skb_reserve(skb, hlen);

	/* set type as fist byte in payload */
	*(u8 *)skb_put(skb, 1) = addr->smctp_type;

	rc = memcpy_from_msg((void *)skb_put(skb, len), msg, len);
	if (rc < 0) {
		kfree_skb(skb);
		return rc;
	}

	/* set up cb */
	cb = __mctp_cb(skb);
	cb->net = addr->smctp_network;

	rc = mctp_local_output(sk, rt, skb, addr->smctp_addr.s_addr,
			       addr->smctp_tag);

	return rc ? : len;
}

static int mctp_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
			int flags)
{
	DECLARE_SOCKADDR(struct sockaddr_mctp *, addr, msg->msg_name);
	struct sock *sk = sock->sk;
	struct sk_buff *skb;
	size_t msglen;
	u8 type;
	int rc;

	if (flags & ~(MSG_DONTWAIT | MSG_TRUNC | MSG_PEEK))
		return -EOPNOTSUPP;

	skb = skb_recv_datagram(sk, flags, flags & MSG_DONTWAIT, &rc);
	if (!skb)
		return rc;

	if (!skb->len) {
		rc = 0;
		goto out_free;
	}

	/* extract message type, remove from data */
	type = *((u8 *)skb->data);
	msglen = skb->len - 1;

	if (len < msglen)
		msg->msg_flags |= MSG_TRUNC;
	else
		len = msglen;

	rc = skb_copy_datagram_msg(skb, 1, msg, len);
	if (rc < 0)
		goto out_free;

	sock_recv_cmsgs(msg, sk, skb);

	if (addr) {
		struct mctp_skb_cb *cb = mctp_cb(skb);
		/* TODO: expand mctp_skb_cb for header fields? */
		struct mctp_hdr *hdr = mctp_hdr(skb);

		addr = msg->msg_name;
		addr->smctp_family = AF_MCTP;
		addr->__smctp_pad0 = 0;
		addr->smctp_network = cb->net;
		addr->smctp_addr.s_addr = hdr->src;
		addr->smctp_type = type;
		addr->smctp_tag = hdr->flags_seq_tag &
					(MCTP_HDR_TAG_MASK | MCTP_HDR_FLAG_TO);
		addr->__smctp_pad1 = 0;
		msg->msg_namelen = sizeof(*addr);
	}

	rc = len;

	if (flags & MSG_TRUNC)
		rc = msglen;

out_free:
	skb_free_datagram(sk, skb);
	return rc;
}

static int mctp_setsockopt(struct socket *sock, int level, int optname,
			   sockptr_t optval, unsigned int optlen)
{
	return -EINVAL;
}

static int mctp_getsockopt(struct socket *sock, int level, int optname,
			   char __user *optval, int __user *optlen)
{
	return -EINVAL;
}

static const struct proto_ops mctp_dgram_ops = {
	.family		= PF_MCTP,
	.release	= mctp_release,
	.bind		= mctp_bind,
	.connect	= sock_no_connect,
	.socketpair	= sock_no_socketpair,
	.accept		= sock_no_accept,
	.getname	= sock_no_getname,
	.poll		= datagram_poll,
	.ioctl		= sock_no_ioctl,
	.gettstamp	= sock_gettstamp,
	.listen		= sock_no_listen,
	.shutdown	= sock_no_shutdown,
	.setsockopt	= mctp_setsockopt,
	.getsockopt	= mctp_getsockopt,
	.sendmsg	= mctp_sendmsg,
	.recvmsg	= mctp_recvmsg,
	.mmap		= sock_no_mmap,
	.sendpage	= sock_no_sendpage,
};

static int mctp_sk_init(struct sock *sk)
{
	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);

	INIT_HLIST_HEAD(&msk->keys);
	return 0;
}

static void mctp_sk_close(struct sock *sk, long timeout)
{
	sk_common_release(sk);
}

static int mctp_sk_hash(struct sock *sk)
{
	struct net *net = sock_net(sk);
	struct sock *existing;
	struct mctp_sock *msk;
	int rc;

	msk = container_of(sk, struct mctp_sock, sk);

	/* Bind lookup runs under RCU, remain live during that. */
	sock_set_flag(sk, SOCK_RCU_FREE);

	mutex_lock(&net->mctp.bind_lock);

	/* Prevent duplicate binds. */
	sk_for_each(existing, &net->mctp.binds) {
		struct mctp_sock *mex =
			container_of(existing, struct mctp_sock, sk);

		if (mex->bind_type == msk->bind_type &&
		    mex->bind_addr == msk->bind_addr &&
		    mex->bind_net == msk->bind_net) {
			rc = -EADDRINUSE;
			goto out;
		}
	}

	sk_add_node_rcu(sk, &net->mctp.binds);
	rc = 0;

out:
	mutex_unlock(&net->mctp.bind_lock);
	return rc;
}

static void mctp_sk_unhash(struct sock *sk)
{
	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
	struct net *net = sock_net(sk);
	struct mctp_sk_key *key;
	struct hlist_node *tmp;
	unsigned long flags;

	/* remove from any type-based binds */
	mutex_lock(&net->mctp.bind_lock);
	sk_del_node_init_rcu(sk);
	mutex_unlock(&net->mctp.bind_lock);

	/* remove tag allocations */
	spin_lock_irqsave(&net->mctp.keys_lock, flags);
	hlist_for_each_entry_safe(key, tmp, &msk->keys, sklist) {
		hlist_del_rcu(&key->sklist);
		hlist_del_rcu(&key->hlist);

		spin_lock(&key->reasm_lock);
		if (key->reasm_head)
			kfree_skb(key->reasm_head);
		key->reasm_head = NULL;
		key->reasm_dead = true;
		spin_unlock(&key->reasm_lock);

		kfree_rcu(key, rcu);
	}
	sock_set_flag(sk, SOCK_DEAD);
	spin_unlock_irqrestore(&net->mctp.keys_lock, flags);

	synchronize_rcu();
}

static void mctp_sk_destruct(struct sock *sk)
{
	skb_queue_purge(&sk->sk_receive_queue);
}

static struct proto mctp_proto = {
	.name		= "MCTP",
	.owner		= THIS_MODULE,
	.obj_size	= sizeof(struct mctp_sock),
	.init		= mctp_sk_init,
	.close		= mctp_sk_close,
	.hash		= mctp_sk_hash,
	.unhash		= mctp_sk_unhash,
};

static int mctp_pf_create(struct net *net, struct socket *sock,
			  int protocol, int kern)
{
	const struct proto_ops *ops;
	struct proto *proto;
	struct sock *sk;
	int rc;

	if (protocol)
		return -EPROTONOSUPPORT;

	/* only datagram sockets are supported */
	if (sock->type != SOCK_DGRAM)
		return -ESOCKTNOSUPPORT;

	proto = &mctp_proto;
	ops = &mctp_dgram_ops;

	sock->state = SS_UNCONNECTED;
	sock->ops = ops;

	sk = sk_alloc(net, PF_MCTP, GFP_KERNEL, proto, kern);
	if (!sk)
		return -ENOMEM;

	sock_init_data(sock, sk);
	sk->sk_destruct = mctp_sk_destruct;

	rc = 0;
	if (sk->sk_prot->init)
		rc = sk->sk_prot->init(sk);

	if (rc)
		goto err_sk_put;

	return 0;

err_sk_put:
	sock_orphan(sk);
	sock_put(sk);
	return rc;
}

static struct net_proto_family mctp_pf = {
	.family = PF_MCTP,
	.create = mctp_pf_create,
	.owner = THIS_MODULE,
};

static __init int mctp_init(void)
{
	int rc;

	/* ensure our uapi tag definitions match the header format */
	BUILD_BUG_ON(MCTP_TAG_OWNER != MCTP_HDR_FLAG_TO);
	BUILD_BUG_ON(MCTP_TAG_MASK != MCTP_HDR_TAG_MASK);

	pr_info("mctp: management component transport protocol core\n");

	rc = sock_register(&mctp_pf);
	if (rc)
		return rc;

	rc = proto_register(&mctp_proto, 0);
	if (rc)
		goto err_unreg_sock;

	rc = mctp_routes_init();
	if (rc)
		goto err_unreg_proto;

	rc = mctp_neigh_init();
	if (rc)
		goto err_unreg_routes;

	rc = mctp_device_init();
	if (rc)
		goto err_unreg_neigh;

	return 0;

err_unreg_neigh:
	mctp_neigh_exit();
err_unreg_routes:
	mctp_routes_exit();
err_unreg_proto:
	proto_unregister(&mctp_proto);
err_unreg_sock:
	sock_unregister(PF_MCTP);

	return rc;
}

static __exit void mctp_exit(void)
{
	mctp_device_exit();
	mctp_neigh_exit();
	mctp_routes_exit();
	proto_unregister(&mctp_proto);
	sock_unregister(PF_MCTP);
}

module_init(mctp_init);
module_exit(mctp_exit);

MODULE_DESCRIPTION("MCTP core");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Jeremy Kerr <jk@codeconstruct.com.au>");

MODULE_ALIAS_NETPROTO(PF_MCTP);
