// SPDX-License-Identifier: GPL-2.0
/*
 * Test functionality of BPF filters with SO_REUSEPORT.  This program creates
 * an SO_REUSEPORT receiver group containing one socket per CPU core. It then
 * creates a BPF program that will select a socket from this group based
 * on the core id that receives the packet.  The sending code artificially
 * moves itself to run on different core ids and sends one message from
 * each core.  Since these packets are delivered over loopback, they should
 * arrive on the same core that sent them.  The receiving code then ensures
 * that the packet was received on the socket for the corresponding core id.
 * This entire process is done for several different core id permutations
 * and for each IPv4/IPv6 and TCP/UDP combination.
 */

#define _GNU_SOURCE

#include <arpa/inet.h>
#include <errno.h>
#include <error.h>
#include <linux/filter.h>
#include <linux/in.h>
#include <linux/unistd.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>

static const int PORT = 8888;

static void build_rcv_group(int *rcv_fd, size_t len, int family, int proto)
{
        struct sockaddr_storage addr;
        struct sockaddr_in  *addr4;
        struct sockaddr_in6 *addr6;
        size_t i;
        int opt;

        switch (family) {
        case AF_INET:
                addr4 = (struct sockaddr_in *)&addr;
                addr4->sin_family = AF_INET;
                addr4->sin_addr.s_addr = htonl(INADDR_ANY);
                addr4->sin_port = htons(PORT);
                break;
        case AF_INET6:
                addr6 = (struct sockaddr_in6 *)&addr;
                addr6->sin6_family = AF_INET6;
                addr6->sin6_addr = in6addr_any;
                addr6->sin6_port = htons(PORT);
                break;
        default:
                error(1, 0, "Unsupported family %d", family);
        }

        for (i = 0; i < len; ++i) {
                rcv_fd[i] = socket(family, proto, 0);
                if (rcv_fd[i] < 0)
                        error(1, errno, "failed to create receive socket");

                opt = 1;
                if (setsockopt(rcv_fd[i], SOL_SOCKET, SO_REUSEPORT, &opt,
                               sizeof(opt)))
                        error(1, errno, "failed to set SO_REUSEPORT");

                if (bind(rcv_fd[i], (struct sockaddr *)&addr, sizeof(addr)))
                        error(1, errno, "failed to bind receive socket");

                if (proto == SOCK_STREAM && listen(rcv_fd[i], len * 10))
                        error(1, errno, "failed to listen on receive port");
        }
}

static void attach_bpf(int fd)
{
        struct sock_filter code[] = {
                /* A = raw_smp_processor_id() */
                { BPF_LD  | BPF_W | BPF_ABS, 0, 0, SKF_AD_OFF + SKF_AD_CPU },
                /* return A */
                { BPF_RET | BPF_A, 0, 0, 0 },
        };
        struct sock_fprog p = {
                .len = 2,
                .filter = code,
        };

        if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_REUSEPORT_CBPF, &p, sizeof(p)))
                error(1, errno, "failed to set SO_ATTACH_REUSEPORT_CBPF");
}

static void send_from_cpu(int cpu_id, int family, int proto)
{
        struct sockaddr_storage saddr, daddr;
        struct sockaddr_in  *saddr4, *daddr4;
        struct sockaddr_in6 *saddr6, *daddr6;
        cpu_set_t cpu_set;
        int fd;

        switch (family) {
        case AF_INET:
                saddr4 = (struct sockaddr_in *)&saddr;
                saddr4->sin_family = AF_INET;
                saddr4->sin_addr.s_addr = htonl(INADDR_ANY);
                saddr4->sin_port = 0;

                daddr4 = (struct sockaddr_in *)&daddr;
                daddr4->sin_family = AF_INET;
                daddr4->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
                daddr4->sin_port = htons(PORT);
                break;
        case AF_INET6:
                saddr6 = (struct sockaddr_in6 *)&saddr;
                saddr6->sin6_family = AF_INET6;
                saddr6->sin6_addr = in6addr_any;
                saddr6->sin6_port = 0;

                daddr6 = (struct sockaddr_in6 *)&daddr;
                daddr6->sin6_family = AF_INET6;
                daddr6->sin6_addr = in6addr_loopback;
                daddr6->sin6_port = htons(PORT);
                break;
        default:
                error(1, 0, "Unsupported family %d", family);
        }

        memset(&cpu_set, 0, sizeof(cpu_set));
        CPU_SET(cpu_id, &cpu_set);
        if (sched_setaffinity(0, sizeof(cpu_set), &cpu_set) < 0)
                error(1, errno, "failed to pin to cpu");

        fd = socket(family, proto, 0);
        if (fd < 0)
                error(1, errno, "failed to create send socket");

        if (bind(fd, (struct sockaddr *)&saddr, sizeof(saddr)))
                error(1, errno, "failed to bind send socket");

        if (connect(fd, (struct sockaddr *)&daddr, sizeof(daddr)))
                error(1, errno, "failed to connect send socket");

        if (send(fd, "a", 1, 0) < 0)
                error(1, errno, "failed to send message");

        close(fd);
}

static
void receive_on_cpu(int *rcv_fd, int len, int epfd, int cpu_id, int proto)
{
        struct epoll_event ev;
        int i, fd;
        char buf[8];

        i = epoll_wait(epfd, &ev, 1, -1);
        if (i < 0)
                error(1, errno, "epoll_wait failed");

        if (proto == SOCK_STREAM) {
                fd = accept(ev.data.fd, NULL, NULL);
                if (fd < 0)
                        error(1, errno, "failed to accept");
                i = recv(fd, buf, sizeof(buf), 0);
                close(fd);
        } else {
                i = recv(ev.data.fd, buf, sizeof(buf), 0);
        }

        if (i < 0)
                error(1, errno, "failed to recv");

        for (i = 0; i < len; ++i)
                if (ev.data.fd == rcv_fd[i])
                        break;
        if (i == len)
                error(1, 0, "failed to find socket");
        fprintf(stderr, "send cpu %d, receive socket %d\n", cpu_id, i);
        if (cpu_id != i)
                error(1, 0, "cpu id/receive socket mismatch");
}

static void test(int *rcv_fd, int len, int family, int proto)
{
        struct epoll_event ev;
        int epfd, cpu;

        build_rcv_group(rcv_fd, len, family, proto);
        attach_bpf(rcv_fd[0]);

        epfd = epoll_create(1);
        if (epfd < 0)
                error(1, errno, "failed to create epoll");
        for (cpu = 0; cpu < len; ++cpu) {
                ev.events = EPOLLIN;
                ev.data.fd = rcv_fd[cpu];
                if (epoll_ctl(epfd, EPOLL_CTL_ADD, rcv_fd[cpu], &ev))
                        error(1, errno, "failed to register sock epoll");
        }

        /* Forward iterate */
        for (cpu = 0; cpu < len; ++cpu) {
                send_from_cpu(cpu, family, proto);
                receive_on_cpu(rcv_fd, len, epfd, cpu, proto);
        }

        /* Reverse iterate */
        for (cpu = len - 1; cpu >= 0; --cpu) {
                send_from_cpu(cpu, family, proto);
                receive_on_cpu(rcv_fd, len, epfd, cpu, proto);
        }

        /* Even cores */
        for (cpu = 0; cpu < len; cpu += 2) {
                send_from_cpu(cpu, family, proto);
                receive_on_cpu(rcv_fd, len, epfd, cpu, proto);
        }

        /* Odd cores */
        for (cpu = 1; cpu < len; cpu += 2) {
                send_from_cpu(cpu, family, proto);
                receive_on_cpu(rcv_fd, len, epfd, cpu, proto);
        }

        close(epfd);
        for (cpu = 0; cpu < len; ++cpu)
                close(rcv_fd[cpu]);
}

int main(void)
{
        int *rcv_fd, cpus;

        cpus = sysconf(_SC_NPROCESSORS_ONLN);
        if (cpus <= 0)
                error(1, errno, "failed counting cpus");

        rcv_fd = calloc(cpus, sizeof(int));
        if (!rcv_fd)
                error(1, 0, "failed to allocate array");

        fprintf(stderr, "---- IPv4 UDP ----\n");
        test(rcv_fd, cpus, AF_INET, SOCK_DGRAM);

        fprintf(stderr, "---- IPv6 UDP ----\n");
        test(rcv_fd, cpus, AF_INET6, SOCK_DGRAM);

        fprintf(stderr, "---- IPv4 TCP ----\n");
        test(rcv_fd, cpus, AF_INET, SOCK_STREAM);

        fprintf(stderr, "---- IPv6 TCP ----\n");
        test(rcv_fd, cpus, AF_INET6, SOCK_STREAM);

        free(rcv_fd);

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