backport: add backport for get_net_ns_by_fd()

In mac80211-next a call to get_net_ns_by_fd() has been added in cfg80211 which resides in networking core. This function has been backported such that it will always fail, ie. as it would when CONFIG_NET_NS is not defined. The call was added by:

commit 4b681c82d2f9bef121c912ffcaac89a004af3f2c
Author: Vadim Kochan <[email protected]>
Date: Mon Jan 12 16:34:05 2015 +0200

nl80211: Allow set network namespace by fd

---
This patch replaces the V2 commit which has
Message-ID: <[email protected]>

Changes:
V2
- solve backport using LINUX_BACKPORT macro (Johannes Berg)
V3
- make backport conditional for kernel before 3.20 (Hauke Mehrtens)

---
 backport/backport-include/net/net_namespace.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

index e83b103..0ba7359 100644
@@ -24,4 +24,15 @@ net_ieee802154_lowpan(struct net *net)
 #endif /* LINUX_VERSION_CODE < KERNEL_VERSION(3,15,0) */
 #endif /* CPTCFG_IEEE802154_6LOWPAN */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3,20,0)
+/*
+ * In older kernels we simply fail this function.
+ */
+#define get_net_ns_by_fd	LINUX_BACKPORT(get_net_ns_by_fd)
+static inline struct net *get_net_ns_by_fd(int fd)
+{
+	return ERR_PTR(-EINVAL);
+}
+#endif
+
 #endif	/* _COMPAT_NET_NET_NAMESPACE_H */

1.9.1

Thank you for the patch it was applied to backports.

Hauke