TAP interface misses packets ,I found the reason。

[Z-J-X]

/Dev/net/Tun should not be opened twice. If it is opened twice, the data will be allocated to two FDS
Temporary solution：you can change like this:

[sequoiar]

@Z-J-X it's for multiple-queue. no problem from my using experience. what's your use-case ?

ifr.ifr_flags = IFF_NO_PI | IFF_MULTI_QUEUE;

[Z-J-X]

@sequoiar I wrote a demo program，like this:

#include <viface/viface.hpp>
#include <iostream>
#include <iomanip>
#include <unistd.h>
#include <algorithm>

using namespace std;
int main()
{
    viface::VIface iface("viface%d");

    // Configure interface
    iface.setIPv4Netmask("255.255.255.0");
    iface.setIPv4("192.168.100.11");

    // Bring-up interface
    iface.up();
    std::set<string> stats_set = iface.listStats();

    while (1)
    {
        auto data = iface.receive();
        if (data.size() == 0)
        {
            sleep(1);
            continue;
        }
        std::cout << "receive:" << std::dec << data.size() << std::endl;
        for (int a : data)
        {
            std::cout << std::setiosflags(std::ios::uppercase) << std::hex << std::setw(2) << std::setfill('0') << a << " ";
        }
        std::cout << std::endl;
    }
}

The results may be different on different machines
ping 192.168.100.1 receive
ping 192.168.100.2 not receive
ping 192.168.100.3 receive

Tcpdump shows that the data has reached the Tun / tap device

i use ping to test this program, I found that half of the data could not be received. Then I looked at the source code and found that Tun / tap would be opened twice, I think the data not received will be received by another FD. Therefore, I modified the source code to test, read the data of two FD, and everything is normal.
ps: After modifying the source code, I only carried out the reading test.

you can see issue#6,They have the same problems as me

[Matheus-Garbelini]

Can confirm that applying this fix solves the issue with missing pings and many other IP packets.