Function sock_readhdr

modules/generators/mod_cgid.c:352–421

Read from the socket dealing with incomplete messages and signals. * Returns 0 on success or errno on failure. Stderr fd passed as * auxiliary data from other end is written to *errfd, or else stderr * fileno if not present. */

 * auxiliary data from other end is written to *errfd, or else stderr
 * fileno if not present. */
static apr_status_t sock_readhdr(int fd, int *errfd, void *vbuf, size_t buf_size)
{
    int rc;
#ifndef HAVE_CGID_FDPASSING
    char *buf = vbuf;
    size_t bytes_read = 0;

    if (errfd) *errfd = 0;
    
    do {
        do {
            rc = read(fd, buf + bytes_read, buf_size - bytes_read);
        } while (rc < 0 && errno == EINTR);
        switch(rc) {
        case -1:
            return errno;
        case 0: /* unexpected */
            return ECONNRESET;
        default:
            bytes_read += rc;
        }
    } while (bytes_read < buf_size);

   
#else /* with FD passing */
    struct msghdr msg = {0};
    struct iovec vec = {vbuf, buf_size};
    struct cmsghdr *cmsg;
    union {  /* union to ensure alignment */
        struct cmsghdr cm;
        char buf[CMSG_SPACE(sizeof(int))];
    } u;
    
    msg.msg_iov = &vec;
    msg.msg_iovlen = 1;

    if (errfd) {
        msg.msg_control = u.buf;
        msg.msg_controllen = sizeof(u.buf);
        *errfd = 0;
    }
    
    /* use MSG_WAITALL to skip loop on truncated reads */
    do {
        rc = recvmsg(fd, &msg, MSG_WAITALL);
    } while (rc < 0 && errno == EINTR);

    if (rc == 0) {
        return ECONNRESET;
    }
    else if (rc < 0) {
        return errno;
    }
    else if (rc != buf_size) {
        /* MSG_WAITALL should ensure the recvmsg blocks until the
         * entire length is read, but let's be paranoid. */
        return APR_INCOMPLETE;
    }