static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
			   size_t iovlen, struct nlmsghdr **answer,
			   bool show_rtnl_err, nl_ext_ack_fn_t errfn)
{
	struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
	struct iovec riov;
	struct msghdr msg = {
		.msg_name = &nladdr,
		.msg_namelen = sizeof(nladdr),
		.msg_iov = iov,
		.msg_iovlen = iovlen,
	};
	unsigned int seq = 0;
	struct nlmsghdr *h;
	int i, status;
	char *buf;

	for (i = 0; i < iovlen; i++) {
		h = iov[i].iov_base;
		h->nlmsg_seq = seq = ++rtnl->seq;
		if (answer == NULL)
			h->nlmsg_flags |= NLM_F_ACK;
	}

	status = sendmsg(rtnl->fd, &msg, 0);
	if (status < 0) {
		perror("Cannot talk to rtnetlink");
		return -1;
	}

	/* change msg to use the response iov */
	msg.msg_iov = &riov;
	msg.msg_iovlen = 1;
	i = 0;
	while (1) {
		status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
		++i;

		if (status < 0)
			return status;

		if (msg.msg_namelen != sizeof(nladdr)) {
			fprintf(stderr,
				"sender address length == %d\n",
				msg.msg_namelen);
			exit(1);
		}
		for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
			int len = h->nlmsg_len;
			int l = len - sizeof(*h);

			if (l < 0 || len > status) {
				if (msg.msg_flags & MSG_TRUNC) {
					fprintf(stderr, "Truncated message\n");
					free(buf);
					return -1;
				}
				fprintf(stderr,
					"!!!malformed message: len=%d\n",
					len);
				exit(1);
			}

			if (nladdr.nl_pid != 0 ||
			    h->nlmsg_pid != rtnl->local.nl_pid ||
			    h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
				/* Don't forget to skip that message. */
				status -= NLMSG_ALIGN(len);
				h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
				continue;
			}

			if (h->nlmsg_type == NLMSG_ERROR) {
				struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);

				if (l < sizeof(struct nlmsgerr)) {
					fprintf(stderr, "ERROR truncated\n");
					free(buf);
					return -1;
				}

				if (!err->error)
					/* check messages from kernel */
					nl_dump_ext_ack(h, errfn);
				else {
					errno = -err->error;

					if (rtnl->proto != NETLINK_SOCK_DIAG &&
					    show_rtnl_err)
						rtnl_talk_error(h, err, errfn);
				}

				if (answer)
					*answer = (struct nlmsghdr *)buf;
				else
					free(buf);

				return err->error ? -i : 0;
			}

			if (answer) {
				*answer = (struct nlmsghdr *)buf;
				return 0;
			}

			fprintf(stderr, "Unexpected reply!!!\n");

			status -= NLMSG_ALIGN(len);
			h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
		}
		free(buf);

		if (msg.msg_flags & MSG_TRUNC) {
			fprintf(stderr, "Message truncated\n");
			continue;
		}

		if (status) {
			fprintf(stderr, "!!!Remnant of size %d\n", status);
			exit(1);
		}
	}
}
Unknown