It's been some time since I've looked at the OVPN source code but I found some cool TUN interface flags recently!

Hey all,

I've been busy in life and I haven't had much time to keep up with the development of the OVPN source code and all the commits and everything (it's been a little while since I last posted). I ended up creating a custom framework for my own personal use that is based on the original modifications I did for OpenVPN (multi-threaded, bulk-reads, TCP-only, standard-MTU). I was able to get over a gigabit speeds on my wifi client with this network-wide VPN solution I have now. 

I found these 2 new-to-me parameters for TUN interfaces which are really cool and I didn't know existed (I also didn't see them last time I checked the source code here) - IFF_MULTI_QUEUE | IFF_VNET_HDR. Obviously the multi-queue flag wouldn't work by default here (since it's not multi-threaded) however this other one is pretty nice if you adjust your buffer sizes to be much bigger :)

For example, I was able to read thousands of bytes of data in one call from TUN if you set the below parameters in C:

ifrq.ifr_flags = (IFF_TUN | IFF_NO_PI | IFF_MULTI_QUEUE | IFF_VNET_HDR);
TUNF[z] = open("/dev/net/tun", O_RDWR);
...
erro = ioctl(TUNF[z], TUNSETIFF, &ifrq);
if (erro < 0) { printf("%s ERRO TUNSETIFF [%d]\n", date(), z); }
...
int leng = sizeof(struct virtio_net_hdr);
erro = ioctl(TUNF[z], TUNSETVNETHDRSZ, &leng);
...
if (erro < 0) { printf("%s ERRO TUNSETVNETHDRSZ [%d]\n", date(), z); }
unsigned int offl = (TUN_F_CSUM | TUN_F_TSO4 | TUN_F_TSO6);
...
erro = ioctl(TUNF[z], TUNSETOFFLOAD, offl);
if (erro < 0) { printf("%s ERRO TUNSETOFFLOAD [%d]\n", date(), z); }

I don't know the full history here yet and am still learning but was this option ever considered to be implemented for OpenVPN?

Thanks again for your support and help and time on this open source project!
I still like it way better than WG haha :)

https://fossjon.com/2026/09/03/finally-got-multi-queue-batch-io-linux-kernel-tun-interface-in-c/

Jon C (root)