esp-protocols/components/sock_utils/src/socketpair.c

/*
 * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */
#include <fcntl.h>
#include "lwip/sockets.h"
#include "socketpair.h"
#include "esp_check.h"

#define INVALID_SOCKET (-1)

static const char *TAG = "socket_helpers";

int socketpair(int domain, int type, int protocol, int sv[2])
{
    if (protocol != 0 || type != SOCK_STREAM || domain != AF_UNIX) {
        errno = ENOSYS; // not implemented
        return -1;
    }
    struct sockaddr_storage ss;
    struct sockaddr_in *sa = (struct sockaddr_in *)&ss;
    socklen_t ss_len = sizeof(struct sockaddr_in);
    int fd1 = INVALID_SOCKET;
    int fd2 = INVALID_SOCKET;
    int listenfd = INVALID_SOCKET;
    int ret = 0; // Success

    sa->sin_family = AF_INET;
    sa->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
    sa->sin_port = 0;
    listenfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    ESP_GOTO_ON_FALSE(listenfd != INVALID_SOCKET, -1, err, TAG, "Cannot create listening socket");
    ESP_GOTO_ON_FALSE(listen(listenfd, 1) == 0, -1, err, TAG, "Failed to listen");

    memset(&ss, 0, sizeof(ss));
    ss_len = sizeof(ss);
    ESP_GOTO_ON_FALSE(getsockname(listenfd, (struct sockaddr *)&ss, &ss_len) >= 0, -1, err, TAG, "getsockname failed");

    sa->sin_family = AF_INET;
    sa->sin_addr.s_addr = htonl(INADDR_LOOPBACK);

    fd1 = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    ESP_GOTO_ON_FALSE(fd1 != INVALID_SOCKET, -1, err, TAG, "Cannot create read side socket");
    ESP_GOTO_ON_FALSE(connect(fd1, (struct sockaddr *)&ss, ss_len) >= 0, -1, err, TAG, "Failed to connect fd1");
    fd2 = accept(listenfd, NULL, 0);
    ESP_GOTO_ON_FALSE(fd2 != INVALID_SOCKET, -1, err, TAG, "Failed to accept fd2");

    close(listenfd);
    sv[0] = fd1;
    sv[1] = fd2;
    return ret;

err:
    if (listenfd != INVALID_SOCKET) {
        close(listenfd);
    }
    if (fd1 != INVALID_SOCKET) {
        close(fd1);
    }
    return ret;
}

int pipe(int pipefd[2])
{
    if (socketpair(AF_UNIX, SOCK_STREAM, 0, pipefd) == -1) {
        return -1;
    }
    // Close the unwanted ends to make it a unidirectional pipe
    if (shutdown(pipefd[0], SHUT_WR) == -1 || shutdown(pipefd[1], SHUT_RD) == -1) {
        close(pipefd[0]);
        close(pipefd[1]);
        return -1;
    }
    return 0;
}