git/git

#include "git-compat-util.h"
#include "strbuf.h"
#include "unix-socket.h"

#define DEFAULT_UNIX_STREAM_LISTEN_BACKLOG (5)

static int chdir_len(const char *orig, int len)
{
    char *path = xmemdupz(orig, len);
    int r = chdir(path);
    free(path);
    return r;
}

struct unix_sockaddr_context {
    char *orig_dir;
};

static void unix_sockaddr_cleanup(struct unix_sockaddr_context *ctx)
{
    if (!ctx->orig_dir)
        return;
    /*
     * If we fail, we can't just return an error, since we have
     * moved the cwd of the whole process, which could confuse calling
     * code.  We are better off to just die.
     */
    if (chdir(ctx->orig_dir) < 0)
        die("unable to restore original working directory");
    free(ctx->orig_dir);
}

static int unix_sockaddr_init(struct sockaddr_un *sa, const char *path,
                  struct unix_sockaddr_context *ctx,
                  int disallow_chdir)
{
    int size = strlen(path) + 1;

    ctx->orig_dir = NULL;
    if (size > sizeof(sa->sun_path)) {
        const char *slash;
        const char *dir;
        struct strbuf cwd = STRBUF_INIT;

        if (disallow_chdir) {
            errno = ENAMETOOLONG;
            return -1;
        }

        slash = find_last_dir_sep(path);
        if (!slash) {
            errno = ENAMETOOLONG;
            return -1;
        }

        dir = path;
        path = slash + 1;
        size = strlen(path) + 1;
        if (size > sizeof(sa->sun_path)) {
            errno = ENAMETOOLONG;
            return -1;
        }
        if (strbuf_getcwd(&cwd))
            return -1;
        ctx->orig_dir = strbuf_detach(&cwd, NULL);
        if (chdir_len(dir, slash - dir) < 0)
            return -1;
    }

    memset(sa, 0, sizeof(*sa));
    sa->sun_family = AF_UNIX;
    memcpy(sa->sun_path, path, size);
    return 0;
}

int unix_stream_connect(const char *path, int disallow_chdir)
{
    int fd = -1, saved_errno;
    struct sockaddr_un sa;
    struct unix_sockaddr_context ctx;

    if (unix_sockaddr_init(&sa, path, &ctx, disallow_chdir) < 0)
        return -1;
    fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd < 0)
        goto fail;

    if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0)
        goto fail;
    unix_sockaddr_cleanup(&ctx);
    return fd;

fail:
    saved_errno = errno;
    if (fd != -1)
        close(fd);
    unix_sockaddr_cleanup(&ctx);
    errno = saved_errno;
    return -1;
}

int unix_stream_listen(const char *path,
               const struct unix_stream_listen_opts *opts)
{
    int fd = -1, saved_errno;
    int backlog;
    struct sockaddr_un sa;
    struct unix_sockaddr_context ctx;

    unlink(path);

    if (unix_sockaddr_init(&sa, path, &ctx, opts->disallow_chdir) < 0)
        return -1;
    fd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd < 0)
        goto fail;

    if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0)
        goto fail;

    backlog = opts->listen_backlog_size;
    if (backlog <= 0)
        backlog = DEFAULT_UNIX_STREAM_LISTEN_BACKLOG;
    if (listen(fd, backlog) < 0)
        goto fail;

    unix_sockaddr_cleanup(&ctx);
    return fd;

fail:
    saved_errno = errno;
    if (fd != -1)
        close(fd);
    unix_sockaddr_cleanup(&ctx);
    errno = saved_errno;
    return -1;
}