diff mbox

[1/3] net: Make interface aliases available for general usage

Message ID 1421009571-5279-2-git-send-email-richard@nod.at
State Not Applicable
Delegated to: Pablo Neira
Headers show

Commit Message

Richard Weinberger Jan. 11, 2015, 8:52 p.m. UTC 
Allow interface aliases to be used as regular interfaces.
Such that a command sequence like this one works:
$ ip l set eth0 alias internet
$ ip a s internet
$ tcpdump -n -i internet

Signed-off-by: Richard Weinberger <richard@nod.at>
---
 include/linux/netdevice.h   |  1 +
 include/net/net_namespace.h |  1 +
 net/core/dev.c              | 52 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+)

Comments

Stephen Hemminger Jan. 11, 2015, 10:40 p.m. UTC | #1 
On Sun, 11 Jan 2015 21:52:49 +0100
Richard Weinberger <richard@nod.at> wrote:

> Allow interface aliases to be used as regular interfaces.
> Such that a command sequence like this one works:
> $ ip l set eth0 alias internet
> $ ip a s internet
> $ tcpdump -n -i internet
> 
> Signed-off-by: Richard Weinberger <richard@nod.at>

There is already a ifalias and it is used by SNMP.
But the common practice is to put longer descriptive names which aren't going
to be usable and there is no requirement that they be unique.

I think you can't do this without breaking some of our users.
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Richard Weinberger Jan. 11, 2015, 10:43 p.m. UTC | #2 
Stephen,

Am 11.01.2015 um 23:40 schrieb Stephen Hemminger:
> On Sun, 11 Jan 2015 21:52:49 +0100
> Richard Weinberger <richard@nod.at> wrote:
> 
>> Allow interface aliases to be used as regular interfaces.
>> Such that a command sequence like this one works:
>> $ ip l set eth0 alias internet
>> $ ip a s internet
>> $ tcpdump -n -i internet
>>
>> Signed-off-by: Richard Weinberger <richard@nod.at>
> 
> There is already a ifalias and it is used by SNMP.
> But the common practice is to put longer descriptive names which aren't going
> to be usable and there is no requirement that they be unique.

Actually I'm using ifalias. This patch just exposes it.

> I think you can't do this without breaking some of our users.

My idea was that udev will not set the alias if already one is used.

Thanks,
//richard

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diff mbox

Patch

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 679e6e9..e00b4e2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1493,6 +1493,7 @@  struct net_device {
 	char			name[IFNAMSIZ];
 	struct hlist_node	name_hlist;
 	char 			*ifalias;
+	struct hlist_node	ifalias_hlist;
 	/*
 	 *	I/O specific fields
 	 *	FIXME: Merge these and struct ifmap into one
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 2e8756b8..9fa0939 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -76,6 +76,7 @@  struct net {
 	struct list_head 	dev_base_head;
 	struct hlist_head 	*dev_name_head;
 	struct hlist_head	*dev_index_head;
+	struct hlist_head	*dev_ifalias_head;
 	unsigned int		dev_base_seq;	/* protected by rtnl_mutex */
 	int			ifindex;
 	unsigned int		dev_unreg_count;
diff --git a/net/core/dev.c b/net/core/dev.c
index 683d493..2551b03 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -202,6 +202,14 @@  static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex)
 	return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)];
 }
 
+static inline struct hlist_head *dev_ifalias_hash(struct net *net,
+						  const char *ifalias)
+{
+	unsigned int hash = full_name_hash(ifalias, strnlen(ifalias, IFALIASZ));
+
+	return &net->dev_ifalias_head[hash_32(hash, NETDEV_HASHBITS)];
+}
+
 static inline void rps_lock(struct softnet_data *sd)
 {
 #ifdef CONFIG_RPS
@@ -228,6 +236,9 @@  static void list_netdevice(struct net_device *dev)
 	hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
 	hlist_add_head_rcu(&dev->index_hlist,
 			   dev_index_hash(net, dev->ifindex));
+	if (dev->ifalias)
+		hlist_add_head_rcu(&dev->ifalias_hlist,
+			   dev_ifalias_hash(net, dev->ifalias));
 	write_unlock_bh(&dev_base_lock);
 
 	dev_base_seq_inc(net);
@@ -245,6 +256,8 @@  static void unlist_netdevice(struct net_device *dev)
 	list_del_rcu(&dev->dev_list);
 	hlist_del_rcu(&dev->name_hlist);
 	hlist_del_rcu(&dev->index_hlist);
+	if (dev->ifalias)
+		hlist_del_rcu(&dev->ifalias_hlist);
 	write_unlock_bh(&dev_base_lock);
 
 	dev_base_seq_inc(dev_net(dev));
@@ -679,6 +692,11 @@  struct net_device *__dev_get_by_name(struct net *net, const char *name)
 		if (!strncmp(dev->name, name, IFNAMSIZ))
 			return dev;
 
+	head = dev_ifalias_hash(net, name);
+	hlist_for_each_entry(dev, head, ifalias_hlist)
+		if (dev->ifalias && !strncmp(dev->ifalias, name, IFALIASZ))
+			return dev;
+
 	return NULL;
 }
 EXPORT_SYMBOL(__dev_get_by_name);
@@ -704,6 +722,11 @@  struct net_device *dev_get_by_name_rcu(struct net *net, const char *name)
 		if (!strncmp(dev->name, name, IFNAMSIZ))
 			return dev;
 
+	head = dev_ifalias_hash(net, name);
+	hlist_for_each_entry_rcu(dev, head, ifalias_hlist)
+		if (dev->ifalias && !strncmp(dev->ifalias, name, IFALIASZ))
+			return dev;
+
 	return NULL;
 }
 EXPORT_SYMBOL(dev_get_by_name_rcu);
@@ -1169,6 +1192,20 @@  rollback:
 	return err;
 }
 
+static void __hlist_del_alias(struct net_device *dev)
+{
+	write_lock_bh(&dev_base_lock);
+	hlist_del_rcu(&dev->ifalias_hlist);
+	write_unlock_bh(&dev_base_lock);
+}
+
+static void __hlist_add_alias(struct net_device *dev)
+{
+	write_lock_bh(&dev_base_lock);
+	hlist_add_head_rcu(&dev->ifalias_hlist, dev_ifalias_hash(dev_net(dev), dev->ifalias));
+	write_unlock_bh(&dev_base_lock);
+}
+
 /**
  *	dev_set_alias - change ifalias of a device
  *	@dev: device
@@ -1189,15 +1226,24 @@  int dev_set_alias(struct net_device *dev, const char *alias, size_t len)
 	if (!len) {
 		kfree(dev->ifalias);
 		dev->ifalias = NULL;
+		__hlist_del_alias(dev);
 		return 0;
 	}
 
 	new_ifalias = krealloc(dev->ifalias, len + 1, GFP_KERNEL);
 	if (!new_ifalias)
 		return -ENOMEM;
+
+	if (dev->ifalias) {
+		__hlist_del_alias(dev);
+		synchronize_rcu();
+	}
+
 	dev->ifalias = new_ifalias;
 
 	strlcpy(dev->ifalias, alias, len+1);
+	__hlist_add_alias(dev);
+
 	return len;
 }
 
@@ -7150,8 +7196,14 @@  static int __net_init netdev_init(struct net *net)
 	if (net->dev_index_head == NULL)
 		goto err_idx;
 
+	net->dev_ifalias_head = netdev_create_hash();
+	if (net->dev_ifalias_head == NULL)
+		goto err_alias;
+
 	return 0;
 
+err_alias:
+	kfree(net->dev_index_head);
 err_idx:
 	kfree(net->dev_name_head);
 err_name: