rmnetctl: add getlink library API and CLI option

Add support for the RTM_GETLINK message in order to retrieve the
configuration of an RmNet device after it has been created.

Change-Id: I7de75c461ab1201a0856911348acef939d3ef172
Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>

rmnetctl/cli/rmnetcli.c

@@ -2,7 +2,7 @@
 
 			R M N E T C L I . C
 
-Copyright (c) 2013-2015, 2017-2018 The Linux Foundation. All rights reserved.
+Copyright (c) 2013-2015, 2017-2019 The Linux Foundation. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
@@ -218,6 +218,7 @@ static void rmnet_api_usage(void)
 	printf(_2TABS" <vnd>                   string - vnd device_name");
 	printf(_2TABS" <vnd id>                int - new vnd id");
 	printf(_2TABS" <flags>                 int - new flag config\n\n");
+	printf("rmnetcli -n getlink <dev_name>           Get device config\n\n");
 	printf("rmnetcli -n dellink <dev_name>           Delete a vnd");
 	printf(_2TABS"                         by inputting dev name\n\n");
 	printf("rmnetcli -n bridgelink  <dev_name>       Bridge a vnd and a dev");
@@ -359,6 +360,19 @@ static int rmnet_api_call(int argc, char *argv[])
 							    &error_number,
 							    _STRTOI32(argv[3]),
 							    _STRTOI32(argv[4]));
+		} else if (!strcmp(*argv, "getlink")) {
+			_RMNETCLI_CHECKNULL(argv[1]);
+			uint32_t flags = 0;
+			uint16_t mux_id = 0;
+
+			return_code = rtrmnet_ctl_getvnd(handle, argv[1],
+							 &error_number,
+							 &mux_id, &flags);
+			if (return_code == RMNETCTL_API_SUCCESS) {
+				printf("Configuration for device %s:\n", argv[1]);
+				printf("\tMux id: %d\n", mux_id);
+				printf("\tData format: 0x%04x\n", flags);
+			}
 		} else if (!strcmp(*argv, "dellink")) {
 			_RMNETCLI_CHECKNULL(argv[1]);
 				return_code = rtrmnet_ctl_delvnd(handle, argv[1],

rmnetctl/inc/librmnetctl.h

@@ -591,6 +591,23 @@ int rtrmnet_ctl_changevnd(rmnetctl_hndl_t *hndl, char *devname, char *vndname,
 			  uint16_t *error_code, uint8_t  index,
 			  uint32_t flagconfig);
 
+/* @brief Public API to retrieve configuration of a virtual device node
+ * @details Message type is RTM_GETLINK
+ * @param hndl RmNet handle for the Netlink message
+ * @param vndname Name of virtual device to query
+ * @param error_code Status code of this operation returned from the kernel
+ * @param mux_id Where to store the value of the node's mux id
+ * @param flagconfig Where to store the value of the node's data format flags
+ * @return RMNETCTL_SUCCESS if successful
+ * @return RMNETCTL_LIB_ERR if there was a library error. Check error_code
+ * @return RMNETCTL_KERNEL_ERR if there was an error in the kernel.
+ * Check error_code
+ * @return RMNETCTL_INVALID_ARF if invalid arguments were passed to the API
+ */
+int rtrmnet_ctl_getvnd(rmnetctl_hndl_t *hndl, char *vndname,
+		       uint16_t *error_code, uint16_t *mux_id,
+		       uint32_t *flagconfig);
+
 /* @brief Public API to bridge a vnd and device
  * @details Message type is RTM_NEWLINK
  * @param hndl RmNet handle for the Netlink message

rmnetctl/src/librmnetctl.c

@@ -1110,6 +1110,31 @@ static void rta_nested_end(struct nlmsg *req, struct rtattr *start)
 	start->rta_len = (char *)NLMSG_TAIL(&req->nl_addr) - (char *)start;
 }
 
+static void rta_parse(struct rtattr **tb, int maxtype, struct rtattr *head,
+		      int len)
+{
+	struct rtattr *rta;
+
+	memset(tb, 0, sizeof(struct rtattr *) * maxtype);
+	for (rta = head; RTA_OK(rta, len);
+	     rta = RTA_NEXT(rta, len)) {
+		__u16 type = rta->rta_type & NLA_TYPE_MASK;
+
+		if (type > 0 && type <= maxtype)
+			tb[type] = rta;
+	}
+}
+
+static struct rtattr *rta_find(struct rtattr *rta, int attrlen, uint16_t type)
+{
+	for (; RTA_OK(rta, attrlen); rta = RTA_NEXT(rta, attrlen)) {
+		if (rta->rta_type == (type & NLA_TYPE_MASK))
+			return rta;
+	}
+
+	return NULL;
+}
+
 /* @brief Fill a Netlink messages with the necessary common RTAs for creating a
  * RTM_NEWLINK message for creating or changing rmnet devices.
  * @param *req The netlink message
@@ -1465,6 +1490,97 @@ int rtrmnet_ctl_changevnd(rmnetctl_hndl_t *hndl, char *devname, char *vndname,
 	return rmnet_get_ack(hndl, error_code);
 }
 
+int rtrmnet_ctl_getvnd(rmnetctl_hndl_t *hndl, char *vndname,
+		       uint16_t *error_code, uint16_t *mux_id,
+		       uint32_t *flagconfig)
+{
+	struct nlmsg req;
+	struct nlmsghdr *resp;
+	struct rtattr *attrs, *linkinfo, *datainfo;
+	struct rtattr *tb[IFLA_VLAN_MAX + 1];
+	unsigned int devindex = 0;
+	int resp_len;
+
+	memset(&req, 0, sizeof(req));
+
+	if (!hndl || !vndname || !error_code || !(mux_id || flagconfig) ||
+	    _rmnetctl_check_dev_name(vndname))
+		return RMNETCTL_INVALID_ARG;
+
+	req.nl_addr.nlmsg_type = RTM_GETLINK;
+	req.nl_addr.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	req.nl_addr.nlmsg_flags = NLM_F_REQUEST;
+	req.nl_addr.nlmsg_seq = hndl->transaction_id;
+	hndl->transaction_id++;
+
+	/* Get index of vndname */
+	devindex = if_nametoindex(vndname);
+	if (devindex == 0) {
+		*error_code = errno;
+		return RMNETCTL_KERNEL_ERR;
+	}
+
+	req.ifmsg.ifi_index = devindex;
+	if (send(hndl->netlink_fd, &req, req.nl_addr.nlmsg_len, 0) < 0) {
+		*error_code = RMNETCTL_API_ERR_MESSAGE_SEND;
+		return RMNETCTL_LIB_ERR;
+	}
+
+	resp_len = recv(hndl->netlink_fd, NULL, 0, MSG_PEEK | MSG_TRUNC);
+	if (resp_len < 0) {
+		*error_code = errno;
+		return RMNETCTL_API_ERR_MESSAGE_RECEIVE;
+	}
+
+	resp = malloc((size_t)resp_len);
+	if (!resp) {
+		*error_code = errno;
+		return RMNETCTL_LIB_ERR;
+	}
+
+	resp_len = recv(hndl->netlink_fd, (char *)resp, (size_t)resp_len, 0);
+	if (resp_len < 0) {
+		*error_code = errno;
+		free(resp);
+		return RMNETCTL_API_ERR_MESSAGE_RECEIVE;
+	}
+
+	/* Parse out the RT attributes */
+	attrs = (struct rtattr *)((char *)NLMSG_DATA(resp) +
+				  NLMSG_ALIGN(sizeof(req.ifmsg)));
+	linkinfo = rta_find(attrs, NLMSG_PAYLOAD(resp, sizeof(req.ifmsg)),
+			    IFLA_LINKINFO);
+	if (!linkinfo) {
+		free(resp);
+		*error_code = RMNETCTL_API_ERR_RTA_FAILURE;
+		return RMNETCTL_KERNEL_ERR;
+	}
+
+	datainfo = rta_find(RTA_DATA(linkinfo), RTA_PAYLOAD(linkinfo),
+			    IFLA_INFO_DATA);
+	if (!datainfo) {
+		free(resp);
+		*error_code = RMNETCTL_API_ERR_RTA_FAILURE;
+		return RMNETCTL_KERNEL_ERR;
+	}
+
+	/* Parse all the rmnet-specific information from the kernel */
+	rta_parse(tb, IFLA_VLAN_MAX + 1, RTA_DATA(datainfo),
+		  RTA_PAYLOAD(datainfo));
+	if (tb[IFLA_VLAN_ID] && mux_id)
+		*mux_id = *((uint16_t *)RTA_DATA(tb[IFLA_VLAN_ID]));
+	if (tb[IFLA_VLAN_FLAGS] && flagconfig) {
+		struct ifla_vlan_flags *flags;
+
+		flags = (struct ifla_vlan_flags *)
+			 RTA_DATA(tb[IFLA_VLAN_FLAGS]);
+		*flagconfig = flags->flags;
+	}
+
+	free(resp);
+	return RMNETCTL_API_SUCCESS;
+}
+
 int rtrmnet_ctl_bridgevnd(rmnetctl_hndl_t *hndl, char *devname, char *vndname,
 			  uint16_t *error_code)
 {