tipc: convert legacy nl bearer dump to nl compat

Introduce a framework for dumping netlink data from the new netlink
API and formatting it to the old legacy API format. This is done by
looping the dump data and calling a format handler for each entity, in
this case a bearer.

We dump until either all data is dumped or we reach the limited buffer
size of the legacy API. Remember, the legacy API doesn't scale.

In this commit we convert TIPC_CMD_GET_BEARER_NAMES to use the compat
layer.

Signed-off-by: Richard Alpe <[e-mail]>
Reviewed-by: Erik Hugne <[e-mail]>
Reviewed-by: Ying Xue <[e-mail]>
Reviewed-by: Jon Maloy <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/tipc_config.h

···
 		(ntohs(((struct tlv_desc *)tlv)->tlv_type) == exp_type);
 }
 
+static inline int TLV_GET_LEN(struct tlv_desc *tlv)
+{
+	return ntohs(tlv->tlv_len);
+}
+
 static inline int TLV_SET(void *tlv, __u16 type, void *data, __u16 len)
 {
 	struct tlv_desc *tlv_ptr;

net/tipc/bearer.c

···
 	return NULL;
 }
 
-/**
- * tipc_bearer_get_names - record names of bearers in buffer
- */
-struct sk_buff *tipc_bearer_get_names(struct net *net)
-{
-	struct tipc_net *tn = net_generic(net, tipc_net_id);
-	struct sk_buff *buf;
-	struct tipc_bearer *b;
-	int i, j;
-
-	buf = tipc_cfg_reply_alloc(MAX_BEARERS * TLV_SPACE(TIPC_MAX_BEARER_NAME));
-	if (!buf)
-		return NULL;
-
-	for (i = 0; media_info_array[i] != NULL; i++) {
-		for (j = 0; j < MAX_BEARERS; j++) {
-			b = rtnl_dereference(tn->bearer_list[j]);
-			if (!b)
-				continue;
-			if (b->media == media_info_array[i]) {
-				tipc_cfg_append_tlv(buf, TIPC_TLV_BEARER_NAME,
-						    b->name,
-						    strlen(b->name) + 1);
-			}
-		}
-	}
-	return buf;
-}
-
 void tipc_bearer_add_dest(struct net *net, u32 bearer_id, u32 dest)
 {
 	struct tipc_net *tn = net_generic(net, tipc_net_id);

net/tipc/bearer.h

···
 int tipc_l2_send_msg(struct net *net, struct sk_buff *buf,
 		     struct tipc_bearer *b, struct tipc_media_addr *dest);
 
-struct sk_buff *tipc_bearer_get_names(struct net *net);
 void tipc_bearer_add_dest(struct net *net, u32 bearer_id, u32 dest);
 void tipc_bearer_remove_dest(struct net *net, u32 bearer_id, u32 dest);
 struct tipc_bearer *tipc_bearer_find(struct net *net, const char *name);

net/tipc/config.c

···
 		rep_tlv_buf = tipc_nametbl_get(net, req_tlv_area,
 					       req_tlv_space);
 		break;
-	case TIPC_CMD_GET_BEARER_NAMES:
-		rep_tlv_buf = tipc_bearer_get_names(net);
-		break;
 	case TIPC_CMD_GET_MEDIA_NAMES:
 		rep_tlv_buf = tipc_media_get_names();
 		break;

net/tipc/netlink_compat.c

···
 
 #include "core.h"
 #include "config.h"
+#include "bearer.h"
 #include <net/genetlink.h>
 #include <linux/tipc_config.h>
+
+/* The legacy API had an artificial message length limit called
+ * ULTRA_STRING_MAX_LEN.
+ */
+#define ULTRA_STRING_MAX_LEN 32768
+
+#define TIPC_SKB_MAX TLV_SPACE(ULTRA_STRING_MAX_LEN)
+
+#define REPLY_TRUNCATED "<truncated>\n"
+
+struct tipc_nl_compat_msg {
+	u16 cmd;
+	int rep_size;
+	struct sk_buff *rep;
+	struct tlv_desc *req;
+	struct sock *dst_sk;
+};
+
+struct tipc_nl_compat_cmd_dump {
+	int (*dumpit)(struct sk_buff *, struct netlink_callback *);
+	int (*format)(struct tipc_nl_compat_msg *msg, struct nlattr **attrs);
+};
+
+static int tipc_skb_tailroom(struct sk_buff *skb)
+{
+	int tailroom;
+	int limit;
+
+	tailroom = skb_tailroom(skb);
+	limit = TIPC_SKB_MAX - skb->len;
+
+	if (tailroom < limit)
+		return tailroom;
+
+	return limit;
+}
+
+static int tipc_add_tlv(struct sk_buff *skb, u16 type, void *data, u16 len)
+{
+	struct tlv_desc *tlv = (struct tlv_desc *)skb_tail_pointer(skb);
+
+	if (tipc_skb_tailroom(skb) < TLV_SPACE(len))
+		return -EMSGSIZE;
+
+	skb_put(skb, TLV_SPACE(len));
+	tlv->tlv_type = htons(type);
+	tlv->tlv_len = htons(TLV_LENGTH(len));
+	if (len && data)
+		memcpy(TLV_DATA(tlv), data, len);
+
+	return 0;
+}
+
+static struct sk_buff *tipc_tlv_alloc(int size)
+{
+	int hdr_len;
+	struct sk_buff *buf;
+
+	size = TLV_SPACE(size);
+	hdr_len = nlmsg_total_size(GENL_HDRLEN + TIPC_GENL_HDRLEN);
+
+	buf = alloc_skb(hdr_len + size, GFP_KERNEL);
+	if (!buf)
+		return NULL;
+
+	skb_reserve(buf, hdr_len);
+
+	return buf;
+}
+
+static struct sk_buff *tipc_get_err_tlv(char *str)
+{
+	int str_len = strlen(str) + 1;
+	struct sk_buff *buf;
+
+	buf = tipc_tlv_alloc(TLV_SPACE(str_len));
+	if (buf)
+		tipc_add_tlv(buf, TIPC_TLV_ERROR_STRING, str, str_len);
+
+	return buf;
+}
+
+static int __tipc_nl_compat_dumpit(struct tipc_nl_compat_cmd_dump *cmd,
+				   struct tipc_nl_compat_msg *msg,
+				   struct sk_buff *arg)
+{
+	int len = 0;
+	int err;
+	struct sk_buff *buf;
+	struct nlmsghdr *nlmsg;
+	struct netlink_callback cb;
+
+	memset(&cb, 0, sizeof(cb));
+	cb.nlh = (struct nlmsghdr *)arg->data;
+	cb.skb = arg;
+
+	buf = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	buf->sk = msg->dst_sk;
+
+	do {
+		int rem;
+
+		len = (*cmd->dumpit)(buf, &cb);
+
+		nlmsg_for_each_msg(nlmsg, nlmsg_hdr(buf), len, rem) {
+			struct nlattr **attrs;
+
+			err = tipc_nlmsg_parse(nlmsg, &attrs);
+			if (err)
+				goto err_out;
+
+			err = (*cmd->format)(msg, attrs);
+			if (err)
+				goto err_out;
+
+			if (tipc_skb_tailroom(msg->rep) <= 1) {
+				err = -EMSGSIZE;
+				goto err_out;
+			}
+		}
+
+		skb_reset_tail_pointer(buf);
+		buf->len = 0;
+
+	} while (len);
+
+	err = 0;
+
+err_out:
+	kfree_skb(buf);
+
+	if (err == -EMSGSIZE) {
+		/* The legacy API only considered messages filling
+		 * "ULTRA_STRING_MAX_LEN" to be truncated.
+		 */
+		if ((TIPC_SKB_MAX - msg->rep->len) <= 1) {
+			char *tail = skb_tail_pointer(msg->rep);
+
+			if (*tail != '\0')
+				sprintf(tail - sizeof(REPLY_TRUNCATED) - 1,
+					REPLY_TRUNCATED);
+		}
+
+		return 0;
+	}
+
+	return err;
+}
+
+static int tipc_nl_compat_dumpit(struct tipc_nl_compat_cmd_dump *cmd,
+				 struct tipc_nl_compat_msg *msg)
+{
+	int err;
+	struct sk_buff *arg;
+
+	msg->rep = tipc_tlv_alloc(msg->rep_size);
+	if (!msg->rep)
+		return -ENOMEM;
+
+	arg = nlmsg_new(0, GFP_KERNEL);
+	if (!arg) {
+		kfree_skb(msg->rep);
+		return -ENOMEM;
+	}
+
+	err = __tipc_nl_compat_dumpit(cmd, msg, arg);
+	if (err)
+		kfree_skb(msg->rep);
+
+	kfree_skb(arg);
+
+	return err;
+}
+
+static int tipc_nl_compat_bearer_dump(struct tipc_nl_compat_msg *msg,
+				      struct nlattr **attrs)
+{
+	struct nlattr *bearer[TIPC_NLA_BEARER_MAX + 1];
+
+	nla_parse_nested(bearer, TIPC_NLA_BEARER_MAX, attrs[TIPC_NLA_BEARER],
+			 NULL);
+
+	return tipc_add_tlv(msg->rep, TIPC_TLV_BEARER_NAME,
+			    nla_data(bearer[TIPC_NLA_BEARER_NAME]),
+			    nla_len(bearer[TIPC_NLA_BEARER_NAME]));
+}
+
+static int tipc_nl_compat_handle(struct tipc_nl_compat_msg *msg)
+{
+	struct tipc_nl_compat_cmd_dump dump;
+
+	memset(&dump, 0, sizeof(dump));
+
+	switch (msg->cmd) {
+	case TIPC_CMD_GET_BEARER_NAMES:
+		msg->rep_size = MAX_BEARERS * TLV_SPACE(TIPC_MAX_BEARER_NAME);
+		dump.dumpit = tipc_nl_bearer_dump;
+		dump.format = tipc_nl_compat_bearer_dump;
+		return tipc_nl_compat_dumpit(&dump, msg);
+	}
+
+	return -EOPNOTSUPP;
+}
+
+static int tipc_nl_compat_recv(struct sk_buff *skb, struct genl_info *info)
+{
+	int err;
+	int len;
+	struct tipc_nl_compat_msg msg;
+	struct nlmsghdr *req_nlh;
+	struct nlmsghdr *rep_nlh;
+	struct tipc_genlmsghdr *req_userhdr = info->userhdr;
+	struct net *net = genl_info_net(info);
+
+	memset(&msg, 0, sizeof(msg));
+
+	req_nlh = (struct nlmsghdr *)skb->data;
+	msg.req = nlmsg_data(req_nlh) + GENL_HDRLEN + TIPC_GENL_HDRLEN;
+	msg.cmd = req_userhdr->cmd;
+	msg.dst_sk = info->dst_sk;
+
+	if ((msg.cmd & 0xC000) && (!netlink_net_capable(skb, CAP_NET_ADMIN))) {
+		msg.rep = tipc_get_err_tlv(TIPC_CFG_NOT_NET_ADMIN);
+		err = -EACCES;
+		goto send;
+	}
+
+	len = nlmsg_attrlen(req_nlh, GENL_HDRLEN + TIPC_GENL_HDRLEN);
+	if (TLV_GET_LEN(msg.req) && !TLV_OK(msg.req, len)) {
+		msg.rep = tipc_get_err_tlv(TIPC_CFG_NOT_SUPPORTED);
+		err = -EOPNOTSUPP;
+		goto send;
+	}
+
+	err = tipc_nl_compat_handle(&msg);
+	if (err == -EOPNOTSUPP)
+		msg.rep = tipc_get_err_tlv(TIPC_CFG_NOT_SUPPORTED);
+	else if (err == -EINVAL)
+		msg.rep = tipc_get_err_tlv(TIPC_CFG_TLV_ERROR);
+send:
+	if (!msg.rep)
+		return err;
+
+	len = nlmsg_total_size(GENL_HDRLEN + TIPC_GENL_HDRLEN);
+	skb_push(msg.rep, len);
+	rep_nlh = nlmsg_hdr(msg.rep);
+	memcpy(rep_nlh, info->nlhdr, len);
+	rep_nlh->nlmsg_len = msg.rep->len;
+	genlmsg_unicast(net, msg.rep, NETLINK_CB(skb).portid);
+
+	return err;
+}
 
 static int handle_cmd(struct sk_buff *skb, struct genl_info *info)
 {
···
 	return 0;
 }
 
+/* Temporary function to keep functionality throughout the patchset
+ * without having to mess with the global variables and other trickery
+ * of the old API.
+ */
+static int tipc_nl_compat_tmp_wrap(struct sk_buff *skb, struct genl_info *info)
+{
+	struct tipc_genlmsghdr *req = info->userhdr;
+
+	switch (req->cmd) {
+	case TIPC_CMD_GET_BEARER_NAMES:
+		return tipc_nl_compat_recv(skb, info);
+	}
+
+	return handle_cmd(skb, info);
+}
+
 static struct genl_family tipc_genl_compat_family = {
 	.id		= GENL_ID_GENERATE,
 	.name		= TIPC_GENL_NAME,
···
 static struct genl_ops tipc_genl_compat_ops[] = {
 	{
 		.cmd		= TIPC_GENL_CMD,
-		.doit		= handle_cmd,
+		.doit		= tipc_nl_compat_tmp_wrap,
 	},
 };