// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE

#include <stddef.h>
#include <arpa/inet.h>
#include <error.h>
#include <errno.h>
#include <net/if.h>
#include <linux/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <netinet/if_ether.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/udp.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#ifndef ETH_MAX_MTU
#define ETH_MAX_MTU     0xFFFFU
#endif

#ifndef UDP_SEGMENT
#define UDP_SEGMENT             103
#endif

#ifndef UDP_MAX_SEGMENTS
#define UDP_MAX_SEGMENTS        (1 << 6UL)
#endif

#define CONST_MTU_TEST  1500

#define CONST_HDRLEN_V4         (sizeof(struct iphdr) + sizeof(struct udphdr))
#define CONST_HDRLEN_V6         (sizeof(struct ip6_hdr) + sizeof(struct udphdr))

#define CONST_MSS_V4            (CONST_MTU_TEST - CONST_HDRLEN_V4)
#define CONST_MSS_V6            (CONST_MTU_TEST - CONST_HDRLEN_V6)

#define CONST_MAX_SEGS_V4       (ETH_MAX_MTU / CONST_MSS_V4)
#define CONST_MAX_SEGS_V6       (ETH_MAX_MTU / CONST_MSS_V6)

static bool             cfg_do_ipv4;
static bool             cfg_do_ipv6;
static bool             cfg_do_connected;
static bool             cfg_do_connectionless;
static bool             cfg_do_msgmore;
static bool             cfg_do_setsockopt;
static int              cfg_specific_test_id = -1;

static const char       cfg_ifname[] = "lo";
static unsigned short   cfg_port = 9000;

static char buf[ETH_MAX_MTU];

struct testcase {
        int tlen;               /* send() buffer size, may exceed mss */
        bool tfail;             /* send() call is expected to fail */
        int gso_len;            /* mss after applying gso */
        int r_num_mss;          /* recv(): number of calls of full mss */
        int r_len_last;         /* recv(): size of last non-mss dgram, if any */
};

const struct in6_addr addr6 = IN6ADDR_LOOPBACK_INIT;
const struct in_addr addr4 = { .s_addr = __constant_htonl(INADDR_LOOPBACK + 2) };

struct testcase testcases_v4[] = {
        {
                /* no GSO: send a single byte */
                .tlen = 1,
                .r_len_last = 1,
        },
        {
                /* no GSO: send a single MSS */
                .tlen = CONST_MSS_V4,
                .r_num_mss = 1,
        },
        {
                /* no GSO: send a single MSS + 1B: fail */
                .tlen = CONST_MSS_V4 + 1,
                .tfail = true,
        },
        {
                /* send a single MSS: will fall back to no GSO */
                .tlen = CONST_MSS_V4,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = 1,
        },
        {
                /* send a single MSS + 1B */
                .tlen = CONST_MSS_V4 + 1,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = 1,
                .r_len_last = 1,
        },
        {
                /* send exactly 2 MSS */
                .tlen = CONST_MSS_V4 * 2,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = 2,
        },
        {
                /* send 2 MSS + 1B */
                .tlen = (CONST_MSS_V4 * 2) + 1,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = 2,
                .r_len_last = 1,
        },
        {
                /* send MAX segs */
                .tlen = (ETH_MAX_MTU / CONST_MSS_V4) * CONST_MSS_V4,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = (ETH_MAX_MTU / CONST_MSS_V4),
        },

        {
                /* send MAX bytes */
                .tlen = ETH_MAX_MTU - CONST_HDRLEN_V4,
                .gso_len = CONST_MSS_V4,
                .r_num_mss = CONST_MAX_SEGS_V4,
                .r_len_last = ETH_MAX_MTU - CONST_HDRLEN_V4 -
                              (CONST_MAX_SEGS_V4 * CONST_MSS_V4),
        },
        {
                /* send MAX + 1: fail */
                .tlen = ETH_MAX_MTU - CONST_HDRLEN_V4 + 1,
                .gso_len = CONST_MSS_V4,
                .tfail = true,
        },
        {
                /* send a single 1B MSS: will fall back to no GSO */
                .tlen = 1,
                .gso_len = 1,
                .r_num_mss = 1,
        },
        {
                /* send 2 1B segments */
                .tlen = 2,
                .gso_len = 1,
                .r_num_mss = 2,
        },
        {
                /* send 2B + 2B + 1B segments */
                .tlen = 5,
                .gso_len = 2,
                .r_num_mss = 2,
                .r_len_last = 1,
        },
        {
                /* send max number of min sized segments */
                .tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4,
                .gso_len = 1,
                .r_num_mss = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4,
        },
        {
                /* send max number + 1 of min sized segments: fail */
                .tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V4 + 1,
                .gso_len = 1,
                .tfail = true,
        },
        {
                /* EOL */
        }
};

#ifndef IP6_MAX_MTU
#define IP6_MAX_MTU     (ETH_MAX_MTU + sizeof(struct ip6_hdr))
#endif

struct testcase testcases_v6[] = {
        {
                /* no GSO: send a single byte */
                .tlen = 1,
                .r_len_last = 1,
        },
        {
                /* no GSO: send a single MSS */
                .tlen = CONST_MSS_V6,
                .r_num_mss = 1,
        },
        {
                /* no GSO: send a single MSS + 1B: fail */
                .tlen = CONST_MSS_V6 + 1,
                .tfail = true,
        },
        {
                /* send a single MSS: will fall back to no GSO */
                .tlen = CONST_MSS_V6,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = 1,
        },
        {
                /* send a single MSS + 1B */
                .tlen = CONST_MSS_V6 + 1,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = 1,
                .r_len_last = 1,
        },
        {
                /* send exactly 2 MSS */
                .tlen = CONST_MSS_V6 * 2,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = 2,
        },
        {
                /* send 2 MSS + 1B */
                .tlen = (CONST_MSS_V6 * 2) + 1,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = 2,
                .r_len_last = 1,
        },
        {
                /* send MAX segs */
                .tlen = (IP6_MAX_MTU / CONST_MSS_V6) * CONST_MSS_V6,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = (IP6_MAX_MTU / CONST_MSS_V6),
        },

        {
                /* send MAX bytes */
                .tlen = IP6_MAX_MTU - CONST_HDRLEN_V6,
                .gso_len = CONST_MSS_V6,
                .r_num_mss = CONST_MAX_SEGS_V6,
                .r_len_last = IP6_MAX_MTU - CONST_HDRLEN_V6 -
                              (CONST_MAX_SEGS_V6 * CONST_MSS_V6),
        },
        {
                /* send MAX + 1: fail */
                .tlen = IP6_MAX_MTU - CONST_HDRLEN_V6 + 1,
                .gso_len = CONST_MSS_V6,
                .tfail = true,
        },
        {
                /* send a single 1B MSS: will fall back to no GSO */
                .tlen = 1,
                .gso_len = 1,
                .r_num_mss = 1,
        },
        {
                /* send 2 1B segments */
                .tlen = 2,
                .gso_len = 1,
                .r_num_mss = 2,
        },
        {
                /* send 2B + 2B + 1B segments */
                .tlen = 5,
                .gso_len = 2,
                .r_num_mss = 2,
                .r_len_last = 1,
        },
        {
                /* send max number of min sized segments */
                .tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6,
                .gso_len = 1,
                .r_num_mss = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6,
        },
        {
                /* send max number + 1 of min sized segments: fail */
                .tlen = UDP_MAX_SEGMENTS - CONST_HDRLEN_V6 + 1,
                .gso_len = 1,
                .tfail = true,
        },
        {
                /* EOL */
        }
};

static unsigned int get_device_mtu(int fd, const char *ifname)
{
        struct ifreq ifr;

        memset(&ifr, 0, sizeof(ifr));

        strcpy(ifr.ifr_name, ifname);

        if (ioctl(fd, SIOCGIFMTU, &ifr))
                error(1, errno, "ioctl get mtu");

        return ifr.ifr_mtu;
}

static void __set_device_mtu(int fd, const char *ifname, unsigned int mtu)
{
        struct ifreq ifr;

        memset(&ifr, 0, sizeof(ifr));

        ifr.ifr_mtu = mtu;
        strcpy(ifr.ifr_name, ifname);

        if (ioctl(fd, SIOCSIFMTU, &ifr))
                error(1, errno, "ioctl set mtu");
}

static void set_device_mtu(int fd, int mtu)
{
        int val;

        val = get_device_mtu(fd, cfg_ifname);
        fprintf(stderr, "device mtu (orig): %u\n", val);

        __set_device_mtu(fd, cfg_ifname, mtu);
        val = get_device_mtu(fd, cfg_ifname);
        if (val != mtu)
                error(1, 0, "unable to set device mtu to %u\n", val);

        fprintf(stderr, "device mtu (test): %u\n", val);
}

static void set_pmtu_discover(int fd, bool is_ipv4)
{
        int level, name, val;

        if (is_ipv4) {
                level   = SOL_IP;
                name    = IP_MTU_DISCOVER;
                val     = IP_PMTUDISC_DO;
        } else {
                level   = SOL_IPV6;
                name    = IPV6_MTU_DISCOVER;
                val     = IPV6_PMTUDISC_DO;
        }

        if (setsockopt(fd, level, name, &val, sizeof(val)))
                error(1, errno, "setsockopt path mtu");
}

static unsigned int get_path_mtu(int fd, bool is_ipv4)
{
        socklen_t vallen;
        unsigned int mtu;
        int ret;

        vallen = sizeof(mtu);
        if (is_ipv4)
                ret = getsockopt(fd, SOL_IP, IP_MTU, &mtu, &vallen);
        else
                ret = getsockopt(fd, SOL_IPV6, IPV6_MTU, &mtu, &vallen);

        if (ret)
                error(1, errno, "getsockopt mtu");


        fprintf(stderr, "path mtu (read):  %u\n", mtu);
        return mtu;
}

/* very wordy version of system("ip route add dev lo mtu 1500 127.0.0.3/32") */
static void set_route_mtu(int mtu, bool is_ipv4)
{
        struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
        struct nlmsghdr *nh;
        struct rtattr *rta;
        struct rtmsg *rt;
        char data[NLMSG_ALIGN(sizeof(*nh)) +
                  NLMSG_ALIGN(sizeof(*rt)) +
                  NLMSG_ALIGN(RTA_LENGTH(sizeof(addr6))) +
                  NLMSG_ALIGN(RTA_LENGTH(sizeof(int))) +
                  NLMSG_ALIGN(RTA_LENGTH(0) + RTA_LENGTH(sizeof(int)))];
        int fd, ret, alen, off = 0;

        alen = is_ipv4 ? sizeof(addr4) : sizeof(addr6);

        fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
        if (fd == -1)
                error(1, errno, "socket netlink");

        memset(data, 0, sizeof(data));

        nh = (void *)data;
        nh->nlmsg_type = RTM_NEWROUTE;
        nh->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
        off += NLMSG_ALIGN(sizeof(*nh));

        rt = (void *)(data + off);
        rt->rtm_family = is_ipv4 ? AF_INET : AF_INET6;
        rt->rtm_table = RT_TABLE_MAIN;
        rt->rtm_dst_len = alen << 3;
        rt->rtm_protocol = RTPROT_BOOT;
        rt->rtm_scope = RT_SCOPE_UNIVERSE;
        rt->rtm_type = RTN_UNICAST;
        off += NLMSG_ALIGN(sizeof(*rt));

        rta = (void *)(data + off);
        rta->rta_type = RTA_DST;
        rta->rta_len = RTA_LENGTH(alen);
        if (is_ipv4)
                memcpy(RTA_DATA(rta), &addr4, alen);
        else
                memcpy(RTA_DATA(rta), &addr6, alen);
        off += NLMSG_ALIGN(rta->rta_len);

        rta = (void *)(data + off);
        rta->rta_type = RTA_OIF;
        rta->rta_len = RTA_LENGTH(sizeof(int));
        *((int *)(RTA_DATA(rta))) = 1; //if_nametoindex("lo");
        off += NLMSG_ALIGN(rta->rta_len);

        /* MTU is a subtype in a metrics type */
        rta = (void *)(data + off);
        rta->rta_type = RTA_METRICS;
        rta->rta_len = RTA_LENGTH(0) + RTA_LENGTH(sizeof(int));
        off += NLMSG_ALIGN(rta->rta_len);

        /* now fill MTU subtype. Note that it fits within above rta_len */
        rta = (void *)(((char *) rta) + RTA_LENGTH(0));
        rta->rta_type = RTAX_MTU;
        rta->rta_len = RTA_LENGTH(sizeof(int));
        *((int *)(RTA_DATA(rta))) = mtu;

        nh->nlmsg_len = off;

        ret = sendto(fd, data, off, 0, (void *)&nladdr, sizeof(nladdr));
        if (ret != off)
                error(1, errno, "send netlink: %uB != %uB\n", ret, off);

        if (close(fd))
                error(1, errno, "close netlink");

        fprintf(stderr, "route mtu (test): %u\n", mtu);
}

static bool __send_one(int fd, struct msghdr *msg, int flags)
{
        int ret;

        ret = sendmsg(fd, msg, flags);
        if (ret == -1 &&
            (errno == EMSGSIZE || errno == ENOMEM || errno == EINVAL))
                return false;
        if (ret == -1)
                error(1, errno, "sendmsg");
        if (ret != msg->msg_iov->iov_len)
                error(1, 0, "sendto: %d != %llu", ret,
                        (unsigned long long)msg->msg_iov->iov_len);
        if (msg->msg_flags)
                error(1, 0, "sendmsg: return flags 0x%x\n", msg->msg_flags);

        return true;
}

static bool send_one(int fd, int len, int gso_len,
                     struct sockaddr *addr, socklen_t alen)
{
        char control[CMSG_SPACE(sizeof(uint16_t))] = {0};
        struct msghdr msg = {0};
        struct iovec iov = {0};
        struct cmsghdr *cm;

        iov.iov_base = buf;
        iov.iov_len = len;

        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;

        msg.msg_name = addr;
        msg.msg_namelen = alen;

        if (gso_len && !cfg_do_setsockopt) {
                msg.msg_control = control;
                msg.msg_controllen = sizeof(control);

                cm = CMSG_FIRSTHDR(&msg);
                cm->cmsg_level = SOL_UDP;
                cm->cmsg_type = UDP_SEGMENT;
                cm->cmsg_len = CMSG_LEN(sizeof(uint16_t));
                *((uint16_t *) CMSG_DATA(cm)) = gso_len;
        }

        /* If MSG_MORE, send 1 byte followed by remainder */
        if (cfg_do_msgmore && len > 1) {
                iov.iov_len = 1;
                if (!__send_one(fd, &msg, MSG_MORE))
                        error(1, 0, "send 1B failed");

                iov.iov_base++;
                iov.iov_len = len - 1;
        }

        return __send_one(fd, &msg, 0);
}

static int recv_one(int fd, int flags)
{
        int ret;

        ret = recv(fd, buf, sizeof(buf), flags);
        if (ret == -1 && errno == EAGAIN && (flags & MSG_DONTWAIT))
                return 0;
        if (ret == -1)
                error(1, errno, "recv");

        return ret;
}

static void run_one(struct testcase *test, int fdt, int fdr,
                    struct sockaddr *addr, socklen_t alen)
{
        int i, ret, val, mss;
        bool sent;

        fprintf(stderr, "ipv%d tx:%d gso:%d %s\n",
                        addr->sa_family == AF_INET ? 4 : 6,
                        test->tlen, test->gso_len,
                        test->tfail ? "(fail)" : "");

        val = test->gso_len;
        if (cfg_do_setsockopt) {
                if (setsockopt(fdt, SOL_UDP, UDP_SEGMENT, &val, sizeof(val)))
                        error(1, errno, "setsockopt udp segment");
        }

        sent = send_one(fdt, test->tlen, test->gso_len, addr, alen);
        if (sent && test->tfail)
                error(1, 0, "send succeeded while expecting failure");
        if (!sent && !test->tfail)
                error(1, 0, "send failed while expecting success");
        if (!sent)
                return;

        if (test->gso_len)
                mss = test->gso_len;
        else
                mss = addr->sa_family == AF_INET ? CONST_MSS_V4 : CONST_MSS_V6;


        /* Recv all full MSS datagrams */
        for (i = 0; i < test->r_num_mss; i++) {
                ret = recv_one(fdr, 0);
                if (ret != mss)
                        error(1, 0, "recv.%d: %d != %d", i, ret, mss);
        }

        /* Recv the non-full last datagram, if tlen was not a multiple of mss */
        if (test->r_len_last) {
                ret = recv_one(fdr, 0);
                if (ret != test->r_len_last)
                        error(1, 0, "recv.%d: %d != %d (last)",
                              i, ret, test->r_len_last);
        }

        /* Verify received all data */
        ret = recv_one(fdr, MSG_DONTWAIT);
        if (ret)
                error(1, 0, "recv: unexpected datagram");
}

static void run_all(int fdt, int fdr, struct sockaddr *addr, socklen_t alen)
{
        struct testcase *tests, *test;

        tests = addr->sa_family == AF_INET ? testcases_v4 : testcases_v6;

        for (test = tests; test->tlen; test++) {
                /* if a specific test is given, then skip all others */
                if (cfg_specific_test_id == -1 ||
                    cfg_specific_test_id == test - tests)
                        run_one(test, fdt, fdr, addr, alen);
        }
}

static void run_test(struct sockaddr *addr, socklen_t alen)
{
        struct timeval tv = { .tv_usec = 100 * 1000 };
        int fdr, fdt, val;

        fdr = socket(addr->sa_family, SOCK_DGRAM, 0);
        if (fdr == -1)
                error(1, errno, "socket r");

        if (bind(fdr, addr, alen))
                error(1, errno, "bind");

        /* Have tests fail quickly instead of hang */
        if (setsockopt(fdr, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)))
                error(1, errno, "setsockopt rcv timeout");

        fdt = socket(addr->sa_family, SOCK_DGRAM, 0);
        if (fdt == -1)
                error(1, errno, "socket t");

        /* Do not fragment these datagrams: only succeed if GSO works */
        set_pmtu_discover(fdt, addr->sa_family == AF_INET);

        if (cfg_do_connectionless) {
                set_device_mtu(fdt, CONST_MTU_TEST);
                run_all(fdt, fdr, addr, alen);
        }

        if (cfg_do_connected) {
                set_device_mtu(fdt, CONST_MTU_TEST + 100);
                set_route_mtu(CONST_MTU_TEST, addr->sa_family == AF_INET);

                if (connect(fdt, addr, alen))
                        error(1, errno, "connect");

                val = get_path_mtu(fdt, addr->sa_family == AF_INET);
                if (val != CONST_MTU_TEST)
                        error(1, 0, "bad path mtu %u\n", val);

                run_all(fdt, fdr, addr, 0 /* use connected addr */);
        }

        if (close(fdt))
                error(1, errno, "close t");
        if (close(fdr))
                error(1, errno, "close r");
}

static void run_test_v4(void)
{
        struct sockaddr_in addr = {0};

        addr.sin_family = AF_INET;
        addr.sin_port = htons(cfg_port);
        addr.sin_addr = addr4;

        run_test((void *)&addr, sizeof(addr));
}

static void run_test_v6(void)
{
        struct sockaddr_in6 addr = {0};

        addr.sin6_family = AF_INET6;
        addr.sin6_port = htons(cfg_port);
        addr.sin6_addr = addr6;

        run_test((void *)&addr, sizeof(addr));
}

static void parse_opts(int argc, char **argv)
{
        int c;

        while ((c = getopt(argc, argv, "46cCmst:")) != -1) {
                switch (c) {
                case '4':
                        cfg_do_ipv4 = true;
                        break;
                case '6':
                        cfg_do_ipv6 = true;
                        break;
                case 'c':
                        cfg_do_connected = true;
                        break;
                case 'C':
                        cfg_do_connectionless = true;
                        break;
                case 'm':
                        cfg_do_msgmore = true;
                        break;
                case 's':
                        cfg_do_setsockopt = true;
                        break;
                case 't':
                        cfg_specific_test_id = strtoul(optarg, NULL, 0);
                        break;
                default:
                        error(1, 0, "%s: parse error", argv[0]);
                }
        }
}

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

        if (cfg_do_ipv4)
                run_test_v4();
        if (cfg_do_ipv6)
                run_test_v6();

        fprintf(stderr, "OK\n");
        return 0;
}