Hi Ale, and sorry for very late reply On Thu, Feb 13, 2020 at 12:27:41PM +0100, Alessandro Vesely wrote: > Has that disclaimer always been in libnfnetlink home page[*]? > > It is the first time I see it. > > I have a userspace filter[???] working with it, and it currently works well. > > If I remove -lnfnetlink from the link command, I get just one undefined > reference to symbol 'nfnl_rcvbufsiz'. It is used only if there is a command > line option to set the buffer size to a given size, to avoid enobufs. For the > rest, the daemon uses libnetfilter_queue. > > Should I rewrite that? How? > > > Best > Ale > -- Yes you can code to avoid using nfnl_rcvbufsiz() from libnfnetlink. Thre is no libmnl or libnetfilter_queue function to do it at present, but libmnl/examples/netfilter/nfct-daemon.c has the code. In case you haven't git cloned libmnl, here is a summary: > socklen_t buffersize; // Set by your command-line option Your code likely already has: > struct mnl_socket *nl; > nl = mnl_socket_open(NETLINK_NETFILTER); (after mnl_socket_bind) > setsockopt(mnl_socket_get_fd(nl), SOL_SOCKET, SO_RCVBUFFORCE, // You should > &buffersize, sizeof(socklen_t)); // check the return code (not shown) If you like, you can check how big a buffer the kernel gave you > socklen_t socklen = sizeof buffersize; > socklen_t read_size = 0; > getsockopt(mnl_socket_get_fd(nl), SOL_SOCKET, SO_RCVBUF, &read_size, &socklen); >From testing it seems you get a buffer of twice buffersize bytes. HTH Cheers ... Duncan.
