static void forward_syslog_iovec(Server *s, const struct iovec *iovec, unsigned n_iovec, const struct ucred *ucred, const struct timeval *tv) {

        static const union sockaddr_union sa = {
                .un.sun_family = AF_UNIX,
                .un.sun_path = "/run/systemd/journal/syslog",
        };
        struct msghdr msghdr = {
                .msg_iov = (struct iovec *) iovec,
                .msg_iovlen = n_iovec,
                .msg_name = (struct sockaddr*) &sa.sa,
                .msg_namelen = offsetof(union sockaddr_union, un.sun_path)
                               + strlen("/run/systemd/journal/syslog"),
        };
        struct cmsghdr *cmsg;
        union {
                struct cmsghdr cmsghdr;
                uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
        } control;

        assert(s);
        assert(iovec);
        assert(n_iovec > 0);

        if (ucred) {
                zero(control);
                msghdr.msg_control = &control;
                msghdr.msg_controllen = sizeof(control);

                cmsg = CMSG_FIRSTHDR(&msghdr);
                cmsg->cmsg_level = SOL_SOCKET;
                cmsg->cmsg_type = SCM_CREDENTIALS;
                cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
                memcpy(CMSG_DATA(cmsg), ucred, sizeof(struct ucred));
                msghdr.msg_controllen = cmsg->cmsg_len;
        }

        /* Forward the syslog message we received via /dev/log to
         * /run/systemd/syslog. Unfortunately we currently can't set
         * the SO_TIMESTAMP auxiliary data, and hence we don't. */

        if (sendmsg(s->syslog_fd, &msghdr, MSG_NOSIGNAL) >= 0)
                return;

        /* The socket is full? I guess the syslog implementation is
         * too slow, and we shouldn't wait for that... */
        if (errno == EAGAIN) {
                s->n_forward_syslog_missed++;
                return;
        }

        if (ucred && (errno == ESRCH || errno == EPERM)) {
                struct ucred u;

                /* Hmm, presumably the sender process vanished
                 * by now, or we don't have CAP_SYS_AMDIN, so
                 * let's fix it as good as we can, and retry */

                u = *ucred;
                u.pid = getpid();
                memcpy(CMSG_DATA(cmsg), &u, sizeof(struct ucred));

                if (sendmsg(s->syslog_fd, &msghdr, MSG_NOSIGNAL) >= 0)
                        return;

                if (errno == EAGAIN) {
                        s->n_forward_syslog_missed++;
                        return;
                }
        }

        if (errno != ENOENT)
                log_debug_errno(errno, "Failed to forward syslog message: %m");
}
Unknown