Merge branch 'netlink-mmap-remove'

Florian Westphal says:

====================
netlink: remove mmapped netlink support

As discussed during netconf 2016 in Seville, this series removes
CONFIG_NETLINK_MMAP.

Close to three years after it was merged it has retained several problems
that do not appear to be fixable.

No official netfilter libmnl release contains support for mmap backed netlink
sockets. No openvswitch release makes use of it either.

To use the mmap interface, userspace not only has to probe for mmap netlink
support, it also has to implement a recv/socket receive path in order to
handle messages that exceed the size of an rx ring element (NL_MMAP_STATUS_COPY).

So if there are odd programs out there that attempt to use MMAP netlink
they should continue to work as they already need a socket based code path
to work properly.

The actual revert (first patch) has a list of problems.
The followup patches remove a couple of helpers that are no longer needed
after the revert.

I did a few tests with mmap vs. socket based interface on a 4.4 based
kernel on an i7-4790 box and there are no performance advantages:

loopback, single nfqueue, queueing in -t filter INPUT:
traffic generated by 8 * ping -q -f localhost:
socket backend:
real    0m27.325s
user    0m3.993s
sys     0m23.292s

with mmap ring backend:
real    0m29.054s
user    0m4.924s
sys     0m24.127s

with single tcp stream, unidirectional, loopback mtu set at 1500
(nc localhost discard < /dev/zero > /dev/null):

socket interface:
time nfqdump -b $((8 * 1024 * 1024 * 1024)) -w /dev/null
real    0m15.960s
user    0m1.756s
sys     0m11.143s

mmap ring:
real    0m16.441s
user    0m3.040s
sys     0m13.687s

socket interface nfqdump[1] with --gso option (i.e. MTU is exceeded,
no kernel-side segmentation and checksum fixups) completes in about 5s.

I also tested dumping a conntrack table with 1m entries.
On my box this takes about 2.4 seconds for both mmap and socket backend:

time LD_PRELOAD=../../src/.libs/libmnl.so ./nfct-dump-sk > /dev/null
mnl_cb_run: Success
messages: 1000000
real    0m2.485s
user    0m1.085s
sys     0m1.400s

time LD_PRELOAD=../../src/.libs/libmnl.so ./nfct-dump-mmap > /dev/null
messages: 1000000
real    0m2.451s
user    0m1.124s
sys     0m1.328s

[1] https://git.breakpoint.cc/cgit/fw/nfqdump.git/
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 0 insertions, 12 deletions

diff --git a/include/linux/netfilter/nfnetlink.h b/include/linux/netfilter/nfnetlink.h
index ba0d9789eb6e..1d82dd5e9a08 100644
--- a/include/linux/netfilter/nfnetlink.h
+++ b/include/linux/netfilter/nfnetlink.h
@@ -34,8 +34,6 @@ int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n);
 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n);
 
 int nfnetlink_has_listeners(struct net *net, unsigned int group);
-struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
-				    u32 dst_portid, gfp_t gfp_mask);
 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 		   unsigned int group, int echo, gfp_t flags);
 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error);
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 0b41959aab9f..da14ab61f363 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -69,16 +69,6 @@ extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group)
 extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
 extern int netlink_has_listeners(struct sock *sk, unsigned int group);
 
-extern struct sk_buff *__netlink_alloc_skb(struct sock *ssk, unsigned int size,
-					   unsigned int ldiff, u32 dst_portid,
-					   gfp_t gfp_mask);
-static inline struct sk_buff *
-netlink_alloc_skb(struct sock *ssk, unsigned int size, u32 dst_portid,
-		  gfp_t gfp_mask)
-{
-	return __netlink_alloc_skb(ssk, size, 0, dst_portid, gfp_mask);
-}
-
 extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
 extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
 			     __u32 group, gfp_t allocation);