#include <sys/types.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/usched.h>

#include <arpa/inet.h>
#include <netinet/in.h>

#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static void     mainloop(int, const struct sockaddr_in *, int);

static void
usage(const char *cmd)
{
        fprintf(stderr, "%s -p port [-i n_instance] [-r] [-B]\n", cmd);
        exit(1);
}

static int
create_socket(const struct sockaddr_in *in, int reuseport)
{
        int serv_s, on;

        serv_s = socket(AF_INET, SOCK_STREAM, 0);
        if (serv_s < 0)
                err(1, "socket failed");

        on = 1;
        if (!reuseport) {
                if (setsockopt(serv_s, SOL_SOCKET, SO_REUSEADDR,
                    &on, sizeof(on)) < 0)
                        err(1, "setsockopt(REUSEADDR) failed");
        } else {
                if (setsockopt(serv_s, SOL_SOCKET, SO_REUSEPORT,
                    &on, sizeof(on)) < 0)
                        err(1, "setsockopt(REUSEPORT) failed");
        }

        if (bind(serv_s, (const struct sockaddr *)in, sizeof(*in)) < 0)
                err(1, "bind failed");

        if (listen(serv_s, -1) < 0)
                err(1, "listen failed");
        return serv_s;
}

int
main(int argc, char *argv[])
{
        struct sockaddr_in in;
        int opt, ninst, serv_s, i, reuseport, bindcpu;
        size_t prm_len;

        prm_len = sizeof(ninst);
        if (sysctlbyname("hw.ncpu", &ninst, &prm_len, NULL, 0) != 0)
                err(2, "sysctl hw.ncpu failed");

        memset(&in, 0, sizeof(in));
        in.sin_family = AF_INET;
        in.sin_addr.s_addr = INADDR_ANY;

        bindcpu = 0;
        reuseport = 0;

        while ((opt = getopt(argc, argv, "Bp:i:r")) != -1) {
                switch (opt) {
                case 'p':
                        in.sin_port = htons(atoi(optarg));
                        break;

                case 'i':
                        ninst = atoi(optarg);
                        break;

                case 'r':
                        reuseport = 1;
                        break;

                case 'B':
                        bindcpu = 1;
                        break;

                default:
                        usage(argv[0]);
                }
        }

        if (ninst < 1 || in.sin_port == 0)
                usage(argv[0]);
        if (!reuseport)
                bindcpu = 0;

        serv_s = -1;
        if (!reuseport)
                serv_s = create_socket(&in, 0);

        for (i = 1; i < ninst; ++i) {
                pid_t pid;

                pid = fork();
                if (pid == 0) {
                        mainloop(serv_s, &in, bindcpu);
                        exit(0);
                } else if (pid < 0) {
                        err(1, "fork failed");
                }
        }

        mainloop(serv_s, &in, bindcpu);
        exit(0);
}

static void
mainloop(int serv_s, const struct sockaddr_in *in, int bindcpu)
{
        if (serv_s < 0)
                serv_s = create_socket(in, 1);

        if (bindcpu) {
                socklen_t cpu_len;
                int cpu;

                cpu_len = sizeof(cpu);
                if (getsockopt(serv_s, SOL_SOCKET, SO_CPUHINT,
                    &cpu, &cpu_len) < 0)
                        err(1, "getsockopt(CPUHINT) failed");
                if (cpu >= 0)
                        usched_set(getpid(), USCHED_SET_CPU, &cpu, sizeof(cpu));
        }

        for (;;) {
                int s;

                s = accept(serv_s, NULL, NULL);
                if (s >= 0)
                        close(s);
        }
        /* NEVER REACHED */
}