fastfetch/src/common/netif/netif_linux.c

#include "netif.h"
#include "common/io/io.h"

#include <net/if.h>
#include <stdio.h>

#define FF_STR_INDIR(x) #x
#define FF_STR(x) FF_STR_INDIR(x)

static bool getDefaultRouteIPv4(char iface[IF_NAMESIZE + 1], uint32_t* ifIndex)
{
    FILE* FF_AUTO_CLOSE_FILE netRoute = fopen("/proc/net/route", "r");
    if (!netRoute) return false;

    // skip first line
    FF_UNUSED(fscanf(netRoute, "%*[^\n]\n"));

    unsigned long long destination; //, gateway, flags, refCount, use, metric, mask, mtu, ...
    while (fscanf(netRoute, "%" FF_STR(IF_NAMESIZE) "s%llx%*[^\n]", iface, &destination) == 2)
    {
        if (destination != 0) continue;
        *ifIndex = if_nametoindex(iface);
        return true;
    }
    iface[0] = '\0';
    return false;
}

static bool getDefaultRouteIPv6(char iface[IF_NAMESIZE + 1], uint32_t* ifIndex)
{
    FILE* FF_AUTO_CLOSE_FILE netRoute = fopen("/proc/net/ipv6_route", "r");
    if (!netRoute) return false;

    uint32_t prefixLen;
    //destination, dest_prefix_len, source, src_prefix_len, next hop, metric, ref counter, use counter, flags, iface
    while (fscanf(netRoute, "%*s %x %*s %*s %*s %*s %*s %*s %*s %" FF_STR(IF_NAMESIZE) "s", &prefixLen, iface) == 2)
    {
        if (prefixLen != 0) continue;
        *ifIndex = if_nametoindex(iface);
        return true;
    }
    iface[0] = '\0';
    return false;
}

bool ffNetifGetDefaultRouteImpl(char iface[IF_NAMESIZE + 1], uint32_t* ifIndex)
{
    if (getDefaultRouteIPv4(iface, ifIndex))
        return true;

    return getDefaultRouteIPv6(iface, ifIndex);
}