Hi Everyone, I'm trying to run through the example at https://www.kernel.org/doc/html/latest/networking/tls.html#kernel-tls . I'm working on Fedora 31 x86_64 (fully patched). Running my program results in: $ ./ktls setsockopt failed, 2, No such file or directory I observed: $ cat /proc/sys/net/ipv4/tcp_available_ulp $ Is there a way to enable ULP at boot? Or is this a kernel config option? Or maybe I am doing something else wrong? Below is the sample code. Jeff ============================== #include <stdio.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/socket.h> #include <sys/types.h> #include <linux/tls.h> #include <netinet/ip.h> #include <netinet/tcp.h> int main() { int sock = socket(AF_INET, SOCK_STREAM, 0); if (sock == -1) { printf("socket failed, %d, %s\n", errno, strerror(errno)); return 1; } if (setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls")) == -1 ) { printf("setsockopt failed, %d, %s\n", errno, strerror(errno)); return 1; } close (sock); return 0; }