// SPDX-License-Identifier: GPL-2.0-or-later
/* udp_vu.c - UDP L2 vhost-user management functions
 *
 * Copyright Red Hat
 * Author: Laurent Vivier <lvivier@redhat.com>
 */

#include <unistd.h>
#include <assert.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/udp.h>
#include <stdint.h>
#include <stddef.h>
#include <sys/uio.h>
#include <linux/virtio_net.h>

#include "checksum.h"
#include "util.h"
#include "ip.h"
#include "siphash.h"
#include "inany.h"
#include "passt.h"
#include "pcap.h"
#include "log.h"
#include "vhost_user.h"
#include "udp_internal.h"
#include "flow.h"
#include "flow_table.h"
#include "udp_flow.h"
#include "udp_vu.h"
#include "vu_common.h"

static struct iovec     iov_vu		[VIRTQUEUE_MAX_SIZE];
static struct vu_virtq_element	elem		[VIRTQUEUE_MAX_SIZE];

/**
 * udp_vu_hdrlen() - Sum size of all headers, from UDP to virtio-net
 * @v6:		Set for IPv6 packet
 *
 * Return: total size of virtio-net, Ethernet, IP, and UDP headers
 */
static size_t udp_vu_hdrlen(bool v6)
{
	size_t hdrlen;

	hdrlen = VNET_HLEN + sizeof(struct ethhdr) + sizeof(struct udphdr);

	if (v6)
		hdrlen += sizeof(struct ipv6hdr);
	else
		hdrlen += sizeof(struct iphdr);

	return hdrlen;
}

/**
 * udp_vu_sock_recv() - Receive datagrams from socket into vhost-user buffers
 * @c:		Execution context
 * @iov:	IO vector for the frame (modified on output)
 * @cnt:	Number of IO vector entries (in/out)
 * @vq:		virtqueue to use to receive data
 * @s:		Socket to receive from
 * @v6:		Set for IPv6 connections
 *
 * Return: size of received data, 0 if the datagram
 *         was discarded because the virtqueue is not ready, -1 on error
 */
static ssize_t udp_vu_sock_recv(const struct ctx *c, struct iovec *iov,
				size_t *cnt, struct vu_virtq *vq, int s,
				bool v6)
{
	const struct vu_dev *vdev = c->vdev;
	struct msghdr msg  = { 0 };
	struct iov_tail payload;
	size_t hdrlen;
	ssize_t dlen;
	int iov_cnt;

	ASSERT(!c->no_udp);

	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
		debug("Got UDP packet, but RX virtqueue not usable yet");

		if (recvmsg(s, &msg, MSG_DONTWAIT) < 0)
			debug_perror("Failed to discard datagram");

		*cnt = 0;
		return 0;
	}

	/* compute L2 header length */
	hdrlen = udp_vu_hdrlen(v6);

	vu_init_elem(elem, iov, *cnt);

	iov_cnt = vu_collect(vdev, vq, elem, ARRAY_SIZE(elem),
			     IP_MAX_MTU + ETH_HLEN + VNET_HLEN, NULL);
	if (iov_cnt == 0)
		return -1;

	payload = IOV_TAIL(iov, iov_cnt, hdrlen);

	struct iovec msg_iov[payload.cnt];
	msg.msg_iov = msg_iov;
	msg.msg_iovlen = iov_tail_clone(msg.msg_iov, payload.cnt, &payload);

	/* read data from the socket */
	dlen = recvmsg(s, &msg, 0);
	if (dlen < 0) {
		vu_queue_rewind(vq, iov_cnt);
		return -1;
	}

	/* Pad short frames to ETH_ZLEN */
	if (ETH_ZLEN + VNET_HLEN > dlen + hdrlen) {
		iov_memset(iov, iov_cnt, dlen + hdrlen, 0,
			   ETH_ZLEN + VNET_HLEN - (dlen + hdrlen));
	}
	*cnt = iov_truncate(iov, iov_cnt, dlen + hdrlen);

	vu_set_vnethdr(iov[0].iov_base, *cnt);

	/* release unused buffers */
	vu_queue_rewind(vq, iov_cnt - *cnt);

	return dlen;
}

/**
 * udp_vu_prepare() - Prepare the packet header
 * @c:		Execution context
 * @data:	IO vector tail for the frame
 * @toside:	Address information for one side of the flow
 * @dlen:	Packet data length
 *
 * Return: Layer-4 length
 */
static size_t udp_vu_prepare(const struct ctx *c, const struct iov_tail *data,
			     const struct flowside *toside, ssize_t dlen)
{
	const struct iovec *iov = data->iov;
	struct ethhdr *eh;
	size_t l4len;

	/* ethernet header */
	eh = vu_eth(iov[0].iov_base);

	memcpy(eh->h_dest, c->guest_mac, sizeof(eh->h_dest));
	memcpy(eh->h_source, c->our_tap_mac, sizeof(eh->h_source));

	/* initialize header */
	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
		struct iphdr *iph = vu_ip(iov[0].iov_base);
		struct udp_payload_t *bp = vu_payloadv4(iov[0].iov_base);

		eh->h_proto = htons(ETH_P_IP);

		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_UDP);

		l4len = udp_update_hdr4(iph, bp, toside, dlen, true);
	} else {
		struct ipv6hdr *ip6h = vu_ip(iov[0].iov_base);
		struct udp_payload_t *bp = vu_payloadv6(iov[0].iov_base);

		eh->h_proto = htons(ETH_P_IPV6);

		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_UDP);

		l4len = udp_update_hdr6(ip6h, bp, toside, dlen, true);
	}

	return l4len;
}

/**
 * udp_vu_csum() - Calculate and set checksum for a UDP packet
 * @toside:	Address information for one side of the flow
 * @data:	IO vector tail for the frame
 */
static void udp_vu_csum(const struct flowside *toside,
			const struct iov_tail *data)
{
	const struct in_addr *src4 = inany_v4(&toside->oaddr);
	const struct in_addr *dst4 = inany_v4(&toside->eaddr);
	struct iov_tail payload = *data;
	struct udphdr *uh, uh_storage;
	bool ipv4 = src4 && dst4;

	iov_drop_header(&payload,
			udp_vu_hdrlen(!ipv4) - sizeof(struct udphdr));
	uh = IOV_REMOVE_HEADER(&payload, uh_storage);

	if (ipv4)
		csum_udp4(uh, *src4, *dst4, &payload);
	else
		csum_udp6(uh, &toside->oaddr.a6, &toside->eaddr.a6, &payload);
}

/**
 * udp_vu_sock_to_tap() - Forward datagrams from socket to tap
 * @c:		Execution context
 * @s:		Socket to read data from
 * @n:		Maximum number of datagrams to forward
 * @tosidx:	Flow & side to forward data from @s to
 */
void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx)
{
	const struct flowside *toside = flowside_at_sidx(tosidx);
	bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
	struct vu_dev *vdev = c->vdev;
	struct vu_virtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
	struct iov_tail data;
	int i;

	for (i = 0; i < n; i++) {
		size_t iov_cnt;
		ssize_t dlen;

		iov_cnt = VIRTQUEUE_MAX_SIZE;
		dlen = udp_vu_sock_recv(c, iov_vu, &iov_cnt, vq, s, v6);
		if (dlen < 0)
			break;

		if (iov_cnt > 0) {
			data = IOV_TAIL(iov_vu, iov_cnt, 0);
			udp_vu_prepare(c, &data, toside, dlen);
			if (*c->pcap) {
				udp_vu_csum(toside, &data);
				pcap_iov(data.iov, data.cnt, VNET_HLEN);
			}
			vu_flush(vdev, vq, elem, data.cnt);
		}
	}
}