[PATCH 0/3] net: implement auto-loading of generic netlink modules

[PATCH 0/3] net: implement auto-loading of generic netlink modules

[Neil Horman]

Eric D. recently noted that the drop_monitor module didn't autoload when the
dropwatch user space utility started.  Looking into this I noted that theres no
formal macro set to define module aliases that can be used by a request module
call in the generic netlink family lookup path.  Currenlty the
net-pf-*-proto-*-type-<n> format is used, but the macros which form this expect
<n> to be a well defined integer, which generic netlink doesn't use for family
definitions.  So this series creates a new macro that create a
net-pf-*-proto-*-name format where name can be any arbitrary string, allowing us
to apend family-<x> where x is a generic netlink family name.  With these
macros, we can easily autoload modules that register generic netlink families

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: James Chapman <jchapman@katalix.com>
CC: David Miller <davem@davemloft.net>

[PATCH 1/3] net: add MODULE_ALIAS_NET_PF_PROTO_NAME

[Neil Horman]

The MODULE_ALAIS_NET_PF macro set is missing a variant that allows for the
appending of an arbitrary string to the net-pf-<x>-proto-<y> base.  while
MODULE_ALIAS_NET_PF_PROTO_NAME_TYPE allows an appending of a numerical type, we
need to be able to append a generic string to support generic netlink families
that have neither a fix numberical protocol or type number

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: David Miller <davem@davemloft.net>
---
 include/linux/net.h |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 2d7510f..e9ac2df 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -313,5 +313,8 @@ extern int kernel_sock_shutdown(struct socket *sock,
 	MODULE_ALIAS("net-pf-" __stringify(pf) "-proto-" __stringify(proto) \
 		     "-type-" __stringify(type))
 
+#define MODULE_ALIAS_NET_PF_PROTO_NAME(pf, proto, name) \
+	MODULE_ALIAS("net-pf-" __stringify(pf) "-proto-" __stringify(proto) \
+		     name)
 #endif /* __KERNEL__ */
 #endif	/* _LINUX_NET_H */
-- 
1.7.7.6

[PATCH 2/3] genetlink: Build a generic netlink family module alias

[Neil Horman]

Generic netlink searches for -type- formatted aliases when requesting a module to
fulfill a protocol request (i.e. net-pf-16-proto-16-type-<x>, where x is a type
value).  However generic netlink protocols have no well defined type numbers,
they have string names.  Modify genl_ctrl_getfamily to request an alias in the
format net-pf-16-proto-16-family-<x> instead, where x is a generic string, and
add a macro that builds on the previously added MODULE_ALIAS_NET_PF_PROTO_NAME
macro to allow modules to specifify those generic strings.

Note, l2tp previously hacked together an net-pf-16-proto-16-type-l2tp alias
using the MODULE_ALIAS macro, with these updates we can convert that to use the
PROTO_NAME macro.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: James Chapman <jchapman@katalix.com>
CC: David Miller <davem@davemloft.net>
---
 include/linux/genetlink.h |    3 +++
 net/l2tp/l2tp_netlink.c   |    3 +--
 net/netlink/genetlink.c   |    2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/genetlink.h b/include/linux/genetlink.h
index 73c28de..7a11401 100644
--- a/include/linux/genetlink.h
+++ b/include/linux/genetlink.h
@@ -110,6 +110,9 @@ extern int lockdep_genl_is_held(void);
 #define genl_dereference(p)					\
 	rcu_dereference_protected(p, lockdep_genl_is_held())
 
+#define MODULE_ALIAS_GENL_FAMILY(family)\
+ MODULE_ALIAS_NET_PF_PROTO_NAME(PF_NETLINK, NETLINK_GENERIC, "-family-" family)
+
 #endif /* __KERNEL__ */
 
 #endif	/* __LINUX_GENERIC_NETLINK_H */
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 8577264..ddc553e 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -923,5 +923,4 @@ MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
 MODULE_DESCRIPTION("L2TP netlink");
 MODULE_LICENSE("GPL");
 MODULE_VERSION("1.0");
-MODULE_ALIAS("net-pf-" __stringify(PF_NETLINK) "-proto-" \
-	     __stringify(NETLINK_GENERIC) "-type-" "l2tp");
+MODULE_ALIAS_GENL_FAMILY("l2tp");
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 8340ace..2cc7c1e 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -836,7 +836,7 @@ static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
 #ifdef CONFIG_MODULES
 		if (res == NULL) {
 			genl_unlock();
-			request_module("net-pf-%d-proto-%d-type-%s",
+			request_module("net-pf-%d-proto-%d-family-%s",
 				       PF_NETLINK, NETLINK_GENERIC, name);
 			genl_lock();
 			res = genl_family_find_byname(name);
-- 
1.7.7.6

[PATCH 3/3] drop_monitor: Add module alias to enable automatic module loading

[Neil Horman]

Now that we have module alias macros for generic netlink families, lets use
those to mark modules with the appropriate family names for loading

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: David Miller <davem@davemloft.net>
---
 net/core/drop_monitor.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index 3252e7e..ea5fb9f 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -468,3 +468,4 @@ module_exit(exit_net_drop_monitor);
 
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Neil Horman <nhorman@tuxdriver.com>");
+MODULE_ALIAS_GENL_FAMILY("NET_DM");
-- 
1.7.7.6

Re: [PATCH 0/3] net: implement auto-loading of generic netlink modules

[David Miller]

From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 29 May 2012 15:30:39 -0400

> 
> Eric D. recently noted that the drop_monitor module didn't autoload when the
> dropwatch user space utility started.  Looking into this I noted that theres no
> formal macro set to define module aliases that can be used by a request module
> call in the generic netlink family lookup path.  Currenlty the
> net-pf-*-proto-*-type-<n> format is used, but the macros which form this expect
> <n> to be a well defined integer, which generic netlink doesn't use for family
> definitions.  So this series creates a new macro that create a
> net-pf-*-proto-*-name format where name can be any arbitrary string, allowing us
> to apend family-<x> where x is a generic netlink family name.  With these
> macros, we can easily autoload modules that register generic netlink families
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

Looks great, all applied, thanks Neil.