tcp-nodelay.c

#define _GNU_SOURCE
#include <stdlib.h>
#include <dlfcn.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/tcp.h>
#include <netinet/in.h>

static size_t tcp_nodelay_count;
static size_t tcp_nodelay_errors;

int (*socket_orig)(int domain, int type, int protocol) = NULL;

__attribute__((constructor)) static void socket_init(void)
{
    socket_orig = dlsym(RTLD_NEXT, "socket");
}

int socket(int domain, int type, int protocol)
{
    int fd = socket_orig(domain, type, protocol);
    if (fd < 0) {
        return fd;
    }
    if (type == SOCK_STREAM) {
        int one = 1;

        ++tcp_nodelay_count;
        if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one))) {
            ++tcp_nodelay_errors;
        }
    }
    return fd;
}