// SPDX-License-Identifier: GPL-2.0
#include <error.h>
#include <fcntl.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/tcp.h>
#include <errno.h>

static int cfg_server;
static int cfg_client;
static int cfg_port = 8000;
static struct sockaddr_in6 cfg_addr;
static char *cfg_outfile;

static int parse_address(const char *str, int port, struct sockaddr_in6 *sin6)
{
        int ret;

        sin6->sin6_family = AF_INET6;
        sin6->sin6_port = htons(port);

        ret = inet_pton(sin6->sin6_family, str, &sin6->sin6_addr);
        if (ret != 1) {
                /* fallback to plain IPv4 */
                ret = inet_pton(AF_INET, str, &sin6->sin6_addr.s6_addr32[3]);
                if (ret != 1)
                        return -1;

                /* add ::ffff prefix */
                sin6->sin6_addr.s6_addr32[0] = 0;
                sin6->sin6_addr.s6_addr32[1] = 0;
                sin6->sin6_addr.s6_addr16[4] = 0;
                sin6->sin6_addr.s6_addr16[5] = 0xffff;
        }

        return 0;
}

static void run_server(void)
{
        unsigned long qlen = 32;
        int fd, opt, connfd;
        socklen_t len;
        char buf[64];
        FILE *outfile;

        outfile = fopen(cfg_outfile, "w");
        if (!outfile)
                error(1, errno, "fopen() outfile");

        fd = socket(AF_INET6, SOCK_STREAM, 0);
        if (fd == -1)
                error(1, errno, "socket()");

        opt = 1;
        if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0)
                error(1, errno, "setsockopt(SO_REUSEADDR)");

        if (setsockopt(fd, SOL_TCP, TCP_FASTOPEN, &qlen, sizeof(qlen)) < 0)
                error(1, errno, "setsockopt(TCP_FASTOPEN)");

        if (bind(fd, (struct sockaddr *)&cfg_addr, sizeof(cfg_addr)) < 0)
                error(1, errno, "bind()");

        if (listen(fd, 5) < 0)
                error(1, errno, "listen()");

        len = sizeof(cfg_addr);
        connfd = accept(fd, (struct sockaddr *)&cfg_addr, &len);
        if (connfd < 0)
                error(1, errno, "accept()");

        len = sizeof(opt);
        if (getsockopt(connfd, SOL_SOCKET, SO_INCOMING_NAPI_ID, &opt, &len) < 0)
                error(1, errno, "getsockopt(SO_INCOMING_NAPI_ID)");

        if (read(connfd, buf, 64) < 0)
                error(1, errno, "read()");

        if (fprintf(outfile, "%d\n", opt) < 0)
                error(1, errno, "fprintf()");

        fclose(outfile);
        close(connfd);
        close(fd);
}

static void run_client(void)
{
        int fd, ret;
        char *msg = "Hello, world!";

        fd = socket(AF_INET6, SOCK_STREAM, 0);
        if (fd == -1)
                error(1, errno, "socket()");

        ret = sendto(fd, msg, strlen(msg), MSG_FASTOPEN,
                     (struct sockaddr *)&cfg_addr, sizeof(cfg_addr));
        if (ret < 0)
                error(1, errno, "sendto()");

        close(fd);
}

static void usage(const char *filepath)
{
        error(1, 0, "Usage: %s (-s|-c) -h<server_ip> -p<port> -o<outfile> ", filepath);
}

static void parse_opts(int argc, char **argv)
{
        struct sockaddr_in6 *addr6 = (void *) &cfg_addr;
        char *addr = NULL;
        int ret;
        int c;

        if (argc <= 1)
                usage(argv[0]);

        while ((c = getopt(argc, argv, "sch:p:o:")) != -1) {
                switch (c) {
                case 's':
                        if (cfg_client)
                                error(1, 0, "Pass one of -s or -c");
                        cfg_server = 1;
                        break;
                case 'c':
                        if (cfg_server)
                                error(1, 0, "Pass one of -s or -c");
                        cfg_client = 1;
                        break;
                case 'h':
                        addr = optarg;
                        break;
                case 'p':
                        cfg_port = strtoul(optarg, NULL, 0);
                        break;
                case 'o':
                        cfg_outfile = strdup(optarg);
                        if (!cfg_outfile)
                                error(1, 0, "outfile invalid");
                        break;
                }
        }

        if (cfg_server && addr)
                error(1, 0, "Server cannot have -h specified");

        memset(addr6, 0, sizeof(*addr6));
        addr6->sin6_family = AF_INET6;
        addr6->sin6_port = htons(cfg_port);
        addr6->sin6_addr = in6addr_any;
        if (addr) {
                ret = parse_address(addr, cfg_port, addr6);
                if (ret)
                        error(1, 0, "Client address parse error: %s", addr);
        }
}

int main(int argc, char **argv)
{
        parse_opts(argc, argv);

        if (cfg_server)
                run_server();
        else if (cfg_client)
                run_client();

        return 0;
}