Patch "IB/core: Fix calculation of maximum RoCE MTU" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

IB/core: Fix calculation of maximum RoCE MTU

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-core-fix-calculation-of-maximum-roce-mtu.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Parav Pandit <[email protected]>
Date: Mon, 16 Oct 2017 08:45:16 +0300
Subject: IB/core: Fix calculation of maximum RoCE MTU

From: Parav Pandit <[email protected]>

[ Upstream commit 99260132fde7bddc6e0132ce53da94d1c9ccabcb ]

The original code only took into consideration the largest header possible after the IB_BTH_BYTES. This was incorrect, as the largest possible header size is the largest possible combination of headers we might run into. The new code accounts for all possible headers in the largest possible combination and subtracts that from the MTU to make sure that all packets will fit on the wire.

---
 include/rdma/ib_addr.h |    7 ++++---
 include/rdma/ib_pack.h |   19 +++++++++++--------
 2 files changed, 15 insertions(+), 11 deletions(-)

@@ -245,10 +245,11 @@ static inline void rdma_addr_set_dgid(st
 static inline enum ib_mtu iboe_get_mtu(int mtu)
 {
 	/*
-	 * reduce IB headers from effective IBoE MTU. 28 stands for
-	 * atomic header which is the biggest possible header after BTH
+	 * Reduce IB headers from effective IBoE MTU.
 	 */
-	mtu = mtu - IB_GRH_BYTES - IB_BTH_BYTES - 28;
+	mtu = mtu - (IB_GRH_BYTES + IB_UDP_BYTES + IB_BTH_BYTES +
+		     IB_EXT_XRC_BYTES + IB_EXT_ATOMICETH_BYTES +
+		     IB_ICRC_BYTES);
 
 	if (mtu >= ib_mtu_enum_to_int(IB_MTU_4096))
 		return IB_MTU_4096;

@@ -37,14 +37,17 @@
 #include <uapi/linux/if_ether.h>
 
 enum {
-	IB_LRH_BYTES  = 8,
-	IB_ETH_BYTES  = 14,
-	IB_VLAN_BYTES = 4,
-	IB_GRH_BYTES  = 40,
-	IB_IP4_BYTES  = 20,
-	IB_UDP_BYTES  = 8,
-	IB_BTH_BYTES  = 12,
-	IB_DETH_BYTES = 8
+	IB_LRH_BYTES		= 8,
+	IB_ETH_BYTES		= 14,
+	IB_VLAN_BYTES		= 4,
+	IB_GRH_BYTES		= 40,
+	IB_IP4_BYTES		= 20,
+	IB_UDP_BYTES		= 8,
+	IB_BTH_BYTES		= 12,
+	IB_DETH_BYTES		= 8,
+	IB_EXT_ATOMICETH_BYTES	= 28,
+	IB_EXT_XRC_BYTES	= 4,
+	IB_ICRC_BYTES		= 4
 };
 
 struct ib_field {

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ib-core-don-t-enforce-pkey-security-on-smi-mads.patch queue-4.14/ib-core-bound-check-alternate-path-port-number.patch queue-4.14/ib-core-fix-calculation-of-maximum-roce-mtu.patch queue-4.14/ib-core-fix-use-workqueue-without-wq_mem_reclaim.patch