linux-sg2042/net/l2tp
Johannes Berg 053c095a82 netlink: make nlmsg_end() and genlmsg_end() void
Contrary to common expectations for an "int" return, these functions
return only a positive value -- if used correctly they cannot even
return 0 because the message header will necessarily be in the skb.

This makes the very common pattern of

  if (genlmsg_end(...) < 0) { ... }

be a whole bunch of dead code. Many places also simply do

  return nlmsg_end(...);

and the caller is expected to deal with it.

This also commonly (at least for me) causes errors, because it is very
common to write

  if (my_function(...))
    /* error condition */

and if my_function() does "return nlmsg_end()" this is of course wrong.

Additionally, there's not a single place in the kernel that actually
needs the message length returned, and if anyone needs it later then
it'll be very easy to just use skb->len there.

Remove this, and make the functions void. This removes a bunch of dead
code as described above. The patch adds lines because I did

-	return nlmsg_end(...);
+	nlmsg_end(...);
+	return 0;

I could have preserved all the function's return values by returning
skb->len, but instead I've audited all the places calling the affected
functions and found that none cared. A few places actually compared
the return value with <= 0 in dump functionality, but that could just
be changed to < 0 with no change in behaviour, so I opted for the more
efficient version.

One instance of the error I've made numerous times now is also present
in net/phonet/pn_netlink.c in the route_dumpit() function - it didn't
check for <0 or <=0 and thus broke out of the loop every single time.
I've preserved this since it will (I think) have caused the messages to
userspace to be formatted differently with just a single message for
every SKB returned to userspace. It's possible that this isn't needed
for the tools that actually use this, but I don't even know what they
are so couldn't test that changing this behaviour would be acceptable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-18 01:03:45 -05:00
..
Kconfig l2tp: Call udp_sock_create 2014-07-14 16:12:15 -07:00
Makefile l2tp: introduce L2TPv3 IP encapsulation support for IPv6 2012-05-01 09:30:55 -04:00
l2tp_core.c l2tp: Refactor l2tp core driver to make use of the common UDP tunnel functions 2014-09-19 15:57:15 -04:00
l2tp_core.h l2tp: Add support for zero IPv6 checksums 2014-05-23 16:28:53 -04:00
l2tp_debugfs.c ipv6: make lookups simpler and faster 2013-10-09 00:01:25 -04:00
l2tp_eth.c l2tp_eth: allow to set a specific mac address 2014-11-21 14:16:38 -05:00
l2tp_ip.c new helper: memcpy_from_msg() 2014-11-24 04:28:48 -05:00
l2tp_ip6.c ip_generic_getfrag, udplite_getfrag: switch to passing msghdr 2014-12-09 16:28:22 -05:00
l2tp_netlink.c netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
l2tp_ppp.c new helper: memcpy_from_msg() 2014-11-24 04:28:48 -05:00