/*
 * xdp-util.h -- set of xdp related helpers
 *
 * Copyright (c) 2024, NLnet Labs. All rights reserved.
 *
 * See LICENSE for the license.
 *
 */

#include "config.h"

#ifdef USE_XDP

#include <errno.h>
#include <linux/ethtool.h>
#include <linux/if.h>
#include <linux/sockios.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

/* for the capability modifications */
/* inspired by https://stackoverflow.com/questions/13183327/drop-root-uid-while-retaining-cap-sys-nice#13186076 */
#include <sys/capability.h>

#include "xdp-util.h"

int ethtool_channels_get(char const *ifname) {
        struct ethtool_channels channels;
        struct ifreq ifr;
        int fd, rc;
        uint32_t queue_count = 0;

        fd = socket(AF_INET, SOCK_DGRAM, 0);
        if (fd < 0) {
                return -1;
        }

        channels.cmd = ETHTOOL_GCHANNELS;
        ifr.ifr_data = (void *)&channels;
        strlcpy(ifr.ifr_name, ifname, IFNAMSIZ);
        rc = ioctl(fd, SIOCETHTOOL, &ifr);
        if (rc != 0) {
                if (errno != EOPNOTSUPP) {
                        close(fd);
                        return -errno;
                }
        }

        if (errno == EOPNOTSUPP) {
                queue_count = 1;
        } else {
                /* ethtool_channels offers
                 * max_{rx,tx,other,combined} and
                 * {rx,tx,other,combined}_count
                 *
                 * Maybe check for different variations of rx/tx and combined
         * queues in the future? */
                if (channels.combined_count > 0) {
                        queue_count = channels.combined_count;
                } else if (channels.rx_count > 0) {
                        queue_count = channels.rx_count;
                } else {
                        queue_count = 1;
                }
        }

        close(fd);
        return (int) queue_count;
}

/* CAPABILITY SHENANIGANS */

void set_caps(int unset_setid_caps) {
#define NUM_CAPS_ALL 4
#define NUM_CAPS_NEEDED 2
        cap_t caps;
        const cap_value_t cap_list[NUM_CAPS_ALL] = {
                CAP_BPF,
                /* CAP_SYS_ADMIN, [> SYS_ADMIN needed for xdp_multiprog__get_from_ifindex <] */
                /* CAP_SYS_RESOURCE, */
                CAP_NET_ADMIN,
                /* CAP_NET_RAW, */
                CAP_SETUID,
                CAP_SETGID
        };

        if (!(caps = cap_init()))
                goto out;

        /* set all above capabilities in permitted and effective sets */
        if (cap_set_flag(caps, CAP_EFFECTIVE, NUM_CAPS_ALL, cap_list, CAP_SET))
                goto out;
        if (cap_set_flag(caps, CAP_PERMITTED, NUM_CAPS_ALL, cap_list, CAP_SET))
                goto out;

        /* unset unneeded capabilities */
        if (unset_setid_caps) {
                if (cap_set_flag(caps, CAP_EFFECTIVE, NUM_CAPS_NEEDED, cap_list + NUM_CAPS_NEEDED, CAP_CLEAR))
                        goto out;
                if (cap_set_flag(caps, CAP_PERMITTED, NUM_CAPS_NEEDED, cap_list + NUM_CAPS_NEEDED, CAP_CLEAR))
                        goto out;
        }

        /* set capabilities as configured above to current process */
        if (cap_set_proc(caps))
                goto out;

out:
        cap_free(caps);
}

#endif /* USE_XDP */