net: implement a SO_PROTOCOL getsockoption

Similar to SO_TYPE returning the socket type, SO_PROTOCOL allows to
retrieve the protocol used with a given socket.

I am not quite sure why we have that-many copies of socket.h, and why
the values are not the same on all arches either, but for where hex
numbers dominate, I use 0x1029 for SO_PROTOCOL as that seems to be
the next free unused number across a bunch of operating systems, or
so Google results make me want to believe. SO_PROTOCOL for others
just uses the next free Linux number, 38.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-generic/socket.h b/include/asm-generic/socket.h
index 5d79e409241c..7e24d186616e 100644
--- a/include/asm-generic/socket.h
+++ b/include/asm-generic/socket.h
@@ -60,4 +60,6 @@
 #define SO_TIMESTAMPING         37
 #define SCM_TIMESTAMPING        SO_TIMESTAMPING
 
+#define SO_PROTOCOL             38
+
 #endif /* __ASM_GENERIC_SOCKET_H */