void hv_kvp_onchannelcallback()

in hv_kvp.c [635:746]
70 lines of code
11 McCabe index (conditional complexity)

void hv_kvp_onchannelcallback(void *context)
{
	struct vmbus_channel *channel = context;
	u32 recvlen;
	u64 requestid;

	struct hv_kvp_msg *kvp_msg;

	struct icmsg_hdr *icmsghdrp;
	int kvp_srv_version;
	static enum {NEGO_NOT_STARTED,
		     NEGO_IN_PROGRESS,
		     NEGO_FINISHED} host_negotiatied = NEGO_NOT_STARTED;

	if (kvp_transaction.state < HVUTIL_READY) {
		/*
		 * If userspace daemon is not connected and host is asking
		 * us to negotiate we need to delay to not lose messages.
		 * This is important for Failover IP setting.
		 */
		if (host_negotiatied == NEGO_NOT_STARTED) {
			host_negotiatied = NEGO_IN_PROGRESS;
			schedule_delayed_work(&kvp_host_handshake_work,
				      HV_UTIL_NEGO_TIMEOUT * HZ);
		}
		return;
	}
	if (kvp_transaction.state > HVUTIL_READY)
		return;

	if (vmbus_recvpacket(channel, recv_buffer, HV_HYP_PAGE_SIZE * 4, &recvlen, &requestid)) {
		pr_err_ratelimited("KVP request received. Could not read into recv buf\n");
		return;
	}

	if (!recvlen)
		return;

	/* Ensure recvlen is big enough to read header data */
	if (recvlen < ICMSG_HDR) {
		pr_err_ratelimited("KVP request received. Packet length too small: %d\n",
				   recvlen);
		return;
	}

	icmsghdrp = (struct icmsg_hdr *)&recv_buffer[sizeof(struct vmbuspipe_hdr)];

	if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
		if (vmbus_prep_negotiate_resp(icmsghdrp,
				recv_buffer, recvlen,
				fw_versions, FW_VER_COUNT,
				kvp_versions, KVP_VER_COUNT,
				NULL, &kvp_srv_version)) {
			pr_info("KVP IC version %d.%d\n",
				kvp_srv_version >> 16,
				kvp_srv_version & 0xFFFF);
		}
	} else if (icmsghdrp->icmsgtype == ICMSGTYPE_KVPEXCHANGE) {
		/*
		 * recvlen is not checked against sizeof(struct kvp_msg) because kvp_msg contains
		 * a union of structs and the msg type received is not known. Code using this
		 * struct should provide validation when accessing its fields.
		 */
		kvp_msg = (struct hv_kvp_msg *)&recv_buffer[ICMSG_HDR];

		/*
		 * Stash away this global state for completing the
		 * transaction; note transactions are serialized.
		 */

		kvp_transaction.recv_len = recvlen;
		kvp_transaction.recv_req_id = requestid;
		kvp_transaction.kvp_msg = kvp_msg;

		if (kvp_transaction.state < HVUTIL_READY) {
			/* Userspace is not registered yet */
			kvp_respond_to_host(NULL, HV_E_FAIL);
			return;
		}
		kvp_transaction.state = HVUTIL_HOSTMSG_RECEIVED;

		/*
		 * Get the information from the
		 * user-mode component.
		 * component. This transaction will be
		 * completed when we get the value from
		 * the user-mode component.
		 * Set a timeout to deal with
		 * user-mode not responding.
		 */
		schedule_work(&kvp_sendkey_work);
		schedule_delayed_work(&kvp_timeout_work,
					HV_UTIL_TIMEOUT * HZ);

		return;

	} else {
		pr_err_ratelimited("KVP request received. Invalid msg type: %d\n",
				   icmsghdrp->icmsgtype);
		return;
	}

	icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
		| ICMSGHDRFLAG_RESPONSE;

	vmbus_sendpacket(channel, recv_buffer,
			 recvlen, requestid,
			 VM_PKT_DATA_INBAND, 0);

	host_negotiatied = NEGO_FINISHED;
	hv_poll_channel(kvp_transaction.recv_channel, kvp_poll_wrapper);
}