/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright 2017 6WIND S.A.
 * Copyright 2017 Mellanox Technologies, Ltd
 */

#include <errno.h>
#include <inttypes.h>
#include <linux/netlink.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdbool.h>

#include <rte_malloc.h>
#include <tap_netlink.h>
#include <rte_random.h>

#include "tap_log.h"

/* Compatibility with glibc < 2.24 */
#ifndef SOL_NETLINK
#define SOL_NETLINK     270
#endif

/* Must be quite large to support dumping a huge list of QDISC or filters. */
#define BUF_SIZE (32 * 1024) /* Size of the buffer to receive kernel messages */
#define SNDBUF_SIZE 32768 /* Send buffer size for the netlink socket */
#define RCVBUF_SIZE 32768 /* Receive buffer size for the netlink socket */

struct nested_tail {
        struct rtattr *tail;
        struct nested_tail *prev;
};

/**
 * Initialize a netlink socket for communicating with the kernel.
 *
 * @param nl_groups
 *   Set it to a netlink group value (e.g. RTMGRP_LINK) to receive messages for
 *   specific netlink multicast groups. Otherwise, no subscription will be made.
 *
 * @return
 *   netlink socket file descriptor on success, -1 otherwise.
 */
int
tap_nl_init(uint32_t nl_groups)
{
        int fd, sndbuf_size = SNDBUF_SIZE, rcvbuf_size = RCVBUF_SIZE;
        struct sockaddr_nl local = {
                .nl_family = AF_NETLINK,
                .nl_groups = nl_groups,
        };
#ifdef NETLINK_EXT_ACK
        int one = 1;
#endif

        fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
        if (fd < 0) {
                TAP_LOG(ERR, "Unable to create a netlink socket");
                return -1;
        }
        if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf_size, sizeof(int))) {
                TAP_LOG(ERR, "Unable to set socket buffer send size");
                close(fd);
                return -1;
        }
        if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf_size, sizeof(int))) {
                TAP_LOG(ERR, "Unable to set socket buffer receive size");
                close(fd);
                return -1;
        }

#ifdef NETLINK_EXT_ACK
        /* Ask for extended ACK response. on older kernel will ignore request. */
        setsockopt(fd, SOL_NETLINK, NETLINK_EXT_ACK, &one, sizeof(one));
#endif

        if (bind(fd, (struct sockaddr *)&local, sizeof(local)) < 0) {
                TAP_LOG(ERR, "Unable to bind to the netlink socket");
                close(fd);
                return -1;
        }
        return fd;
}

/**
 * Clean up a netlink socket once all communicating with the kernel is finished.
 *
 * @param[in] nlsk_fd
 *   The netlink socket file descriptor used for communication.
 *
 * @return
 *   0 on success, -1 otherwise.
 */
int
tap_nl_final(int nlsk_fd)
{
        if (close(nlsk_fd)) {
                TAP_LOG(ERR, "Failed to close netlink socket: %s (%d)",
                        strerror(errno), errno);
                return -1;
        }
        return 0;
}

/**
 * Send a message to the kernel on the netlink socket.
 *
 * @param[in] nlsk_fd
 *   The netlink socket file descriptor used for communication.
 * @param[in] nh
 *   The netlink message send to the kernel.
 *
 * @return
 *   the number of sent bytes on success, -1 otherwise.
 */
int
tap_nl_send(int nlsk_fd, struct nlmsghdr *nh)
{
        int send_bytes;

        nh->nlmsg_pid = 0; /* communication with the kernel uses pid 0 */
        nh->nlmsg_seq = (uint32_t)rte_rand();

retry:
        send_bytes = send(nlsk_fd, nh, nh->nlmsg_len, 0);
        if (send_bytes < 0) {
                if (errno == EINTR)
                        goto retry;

                TAP_LOG(ERR, "Failed to send netlink message: %s (%d)",
                        strerror(errno), errno);
                return -1;
        }
        return send_bytes;
}

#ifdef NETLINK_EXT_ACK
static const struct nlattr *
tap_nl_attr_first(const struct nlmsghdr *nh, size_t offset)
{
        return (const struct nlattr *)((const char *)nh + NLMSG_SPACE(offset));
}

static const struct nlattr *
tap_nl_attr_next(const struct nlattr *attr)
{
        return (const struct nlattr *)((const char *)attr
                                       + NLMSG_ALIGN(attr->nla_len));
}

static bool
tap_nl_attr_ok(const struct nlattr *attr, int len)
{
        if (len < (int)sizeof(struct nlattr))
                return false; /* missing header */
        if (attr->nla_len < sizeof(struct nlattr))
                return false; /* attribute length should include itself */
        if ((int)attr->nla_len  > len)
                return false; /* attribute is truncated */
        return true;
}


/* Decode extended errors from kernel */
static void
tap_nl_dump_ext_ack(const struct nlmsghdr *nh, const struct nlmsgerr *err)
{
        const struct nlattr *attr;
        const char *tail = (const char *)nh + NLMSG_ALIGN(nh->nlmsg_len);
        size_t hlen = sizeof(*err);

        /* no TLVs, no extended response */
        if (!(nh->nlmsg_flags & NLM_F_ACK_TLVS))
                return;

        if (!(nh->nlmsg_flags & NLM_F_CAPPED))
                hlen += err->msg.nlmsg_len - NLMSG_HDRLEN;

        for (attr = tap_nl_attr_first(nh, hlen);
             tap_nl_attr_ok(attr, tail - (const char *)attr);
             attr = tap_nl_attr_next(attr)) {
                uint16_t type = attr->nla_type & NLA_TYPE_MASK;

                if (type == NLMSGERR_ATTR_MSG) {
                        const char *msg = (const char *)attr
                                + NLMSG_ALIGN(sizeof(*attr));

                        if (err->error)
                                TAP_LOG(ERR, "%s", msg);
                        else

                                TAP_LOG(WARNING, "%s", msg);
                        break;
                }
        }
}
#else
/*
 * External ACK support was added in Linux kernel 4.17
 * on older kernels, just ignore that part of message
 */
#define tap_nl_dump_ext_ack(nh, err) do { } while (0)
#endif

/**
 * Check that the kernel sends an appropriate ACK in response
 * to an tap_nl_send().
 *
 * @param[in] nlsk_fd
 *   The netlink socket file descriptor used for communication.
 *
 * @return
 *   0 on success, -1 otherwise with errno set.
 */
int
tap_nl_recv_ack(int nlsk_fd)
{
        return tap_nl_recv(nlsk_fd, NULL, NULL);
}

/**
 * Receive a message from the kernel on the netlink socket, following an
 * tap_nl_send().
 *
 * @param[in] nlsk_fd
 *   The netlink socket file descriptor used for communication.
 * @param[in] cb
 *   The callback function to call for each netlink message received.
 * @param[in, out] arg
 *   Custom arguments for the callback.
 *
 * @return
 *   0 on success, -1 otherwise with errno set.
 */
int
tap_nl_recv(int nlsk_fd, int (*cb)(struct nlmsghdr *, void *arg), void *arg)
{
        char buf[BUF_SIZE];
        int multipart = 0;
        int ret = 0;

        do {
                struct nlmsghdr *nh;
                int recv_bytes;

retry:
                recv_bytes = recv(nlsk_fd, buf, sizeof(buf), 0);
                if (recv_bytes < 0) {
                        if (errno == EINTR)
                                goto retry;
                        return -1;
                }

                for (nh = (struct nlmsghdr *)buf;
                     NLMSG_OK(nh, (unsigned int)recv_bytes);
                     nh = NLMSG_NEXT(nh, recv_bytes)) {
                        if (nh->nlmsg_type == NLMSG_ERROR) {
                                struct nlmsgerr *err_data = NLMSG_DATA(nh);

                                tap_nl_dump_ext_ack(nh, err_data);
                                if (err_data->error < 0) {
                                        errno = -err_data->error;
                                        return -1;
                                }
                                /* Ack message. */
                                return 0;
                        }
                        /* Multi-part msgs and their trailing DONE message. */
                        if (nh->nlmsg_flags & NLM_F_MULTI) {
                                if (nh->nlmsg_type == NLMSG_DONE)
                                        return 0;
                                multipart = 1;
                        }
                        if (cb)
                                ret = cb(nh, arg);
                }
        } while (multipart);
        return ret;
}

/**
 * Append a netlink attribute to a message.
 *
 * @param[in, out] nh
 *   The netlink message to parse, received from the kernel.
 * @param[in] type
 *   The type of attribute to append.
 * @param[in] data_len
 *   The length of the data to append.
 * @param[in] data
 *   The data to append.
 */
void
tap_nlattr_add(struct nlmsghdr *nh, unsigned short type,
           unsigned int data_len, const void *data)
{
        /* see man 3 rtnetlink */
        struct rtattr *rta;

        rta = (struct rtattr *)NLMSG_TAIL(nh);
        rta->rta_len = RTA_LENGTH(data_len);
        rta->rta_type = type;
        memcpy(RTA_DATA(rta), data, data_len);
        nh->nlmsg_len = NLMSG_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta->rta_len);
}

/**
 * Append a uint8_t netlink attribute to a message.
 *
 * @param[in, out] nh
 *   The netlink message to parse, received from the kernel.
 * @param[in] type
 *   The type of attribute to append.
 * @param[in] data
 *   The data to append.
 */
void
tap_nlattr_add8(struct nlmsghdr *nh, unsigned short type, uint8_t data)
{
        tap_nlattr_add(nh, type, sizeof(uint8_t), &data);
}

/**
 * Append a uint16_t netlink attribute to a message.
 *
 * @param[in, out] nh
 *   The netlink message to parse, received from the kernel.
 * @param[in] type
 *   The type of attribute to append.
 * @param[in] data
 *   The data to append.
 */
void
tap_nlattr_add16(struct nlmsghdr *nh, unsigned short type, uint16_t data)
{
        tap_nlattr_add(nh, type, sizeof(uint16_t), &data);
}

/**
 * Append a uint16_t netlink attribute to a message.
 *
 * @param[in, out] nh
 *   The netlink message to parse, received from the kernel.
 * @param[in] type
 *   The type of attribute to append.
 * @param[in] data
 *   The data to append.
 */
void
tap_nlattr_add32(struct nlmsghdr *nh, unsigned short type, uint32_t data)
{
        tap_nlattr_add(nh, type, sizeof(uint32_t), &data);
}

/**
 * Start a nested netlink attribute.
 * It must be followed later by a call to tap_nlattr_nested_finish().
 *
 * @param[in, out] msg
 *   The netlink message where to edit the nested_tails metadata.
 * @param[in] type
 *   The nested attribute type to append.
 *
 * @return
 *   -1 if adding a nested netlink attribute failed, 0 otherwise.
 */
int
tap_nlattr_nested_start(struct nlmsg *msg, uint16_t type)
{
        struct nested_tail *tail;

        tail = rte_zmalloc(NULL, sizeof(struct nested_tail), 0);
        if (!tail) {
                TAP_LOG(ERR,
                        "Couldn't allocate memory for nested netlink attribute");
                return -1;
        }

        tail->tail = (struct rtattr *)NLMSG_TAIL(&msg->nh);

        tap_nlattr_add(&msg->nh, type, 0, NULL);

        tail->prev = msg->nested_tails;

        msg->nested_tails = tail;

        return 0;
}

/**
 * End a nested netlink attribute.
 * It follows a call to tap_nlattr_nested_start().
 * In effect, it will modify the nested attribute length to include every bytes
 * from the nested attribute start, up to here.
 *
 * @param[in, out] msg
 *   The netlink message where to edit the nested_tails metadata.
 */
void
tap_nlattr_nested_finish(struct nlmsg *msg)
{
        struct nested_tail *tail = msg->nested_tails;

        tail->tail->rta_len = (char *)NLMSG_TAIL(&msg->nh) - (char *)tail->tail;

        if (tail->prev)
                msg->nested_tails = tail->prev;

        rte_free(tail);
}