batman-adv: add fixes for packet checksum handling

Fixes "hw csum failure" log spam in batman-adv.

patches/packages/routing/0002-batman-adv-add-fixes-for-packet-checksum-handling.patch

+From: Matthias Schiffer <mschiffer@universe-factory.net>
+Date: Mon, 22 Jan 2018 20:41:41 +0100
+Subject: batman-adv: add fixes for packet checksum handling
+
+diff --git a/batman-adv/patches/0001-batman-adv-fix-packet-checksum-in-receive-path.patch b/batman-adv/patches/0001-batman-adv-fix-packet-checksum-in-receive-path.patch
+new file mode 100644
+index 0000000000000000000000000000000000000000..ce1a5345be1405ccf034ab948b2061be46cda090
+--- /dev/null
++++ b/batman-adv/patches/0001-batman-adv-fix-packet-checksum-in-receive-path.patch
+@@ -0,0 +1,44 @@
++From 05cee97344804ffb2a8df87603663a098fd0cb36 Mon Sep 17 00:00:00 2001
++Message-Id: <05cee97344804ffb2a8df87603663a098fd0cb36.1516705934.git.mschiffer@universe-factory.net>
++From: Matthias Schiffer <mschiffer@universe-factory.net>
++Date: Mon, 22 Jan 2018 20:06:51 +0100
++Subject: [PATCH 1/2] batman-adv: fix packet checksum in receive path
++
++eth_type_trans() internally calls skb_pull(), which does not adjust the
++skb checksum; skb_postpull_rcsum() is necessary to avoid log spam of the
++form "bat0: hw csum failure" when packets with CHECKSUM_COMPLETE are
++received.
++
++Note that in usual setups, packets don't reach batman-adv with
++CHECKSUM_COMPLETE (I assume NICs bail out of checksumming when they see
++batadv's ethtype?), which is why the log messages do nor occur on every
++system using batman-adv. I could reproduce this issue by stacking
++batman-adv on top of a VXLAN interface.
++
++Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
++---
++ net/batman-adv/soft-interface.c | 8 +-------
++ 1 file changed, 1 insertion(+), 7 deletions(-)
++
++diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
++index 9f673cdf..6f7ce7a6 100644
++--- a/net/batman-adv/soft-interface.c
+++++ b/net/batman-adv/soft-interface.c
++@@ -451,13 +451,7 @@ void batadv_interface_rx(struct net_device *soft_iface,
++ 
++ 	/* skb->dev & skb->pkt_type are set here */
++ 	skb->protocol = eth_type_trans(skb, soft_iface);
++-
++-	/* should not be necessary anymore as we use skb_pull_rcsum()
++-	 * TODO: please verify this and remove this TODO
++-	 * -- Dec 21st 2009, Simon Wunderlich
++-	 */
++-
++-	/* skb->ip_summed = CHECKSUM_UNNECESSARY; */
+++	skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN);
++ 
++ 	batadv_inc_counter(bat_priv, BATADV_CNT_RX);
++ 	batadv_add_counter(bat_priv, BATADV_CNT_RX_BYTES,
++-- 
++2.16.1
++
+diff --git a/batman-adv/patches/0002-batman-adv-invalidate-checksum-on-fragment-reassembl.patch b/batman-adv/patches/0002-batman-adv-invalidate-checksum-on-fragment-reassembl.patch
+new file mode 100644
+index 0000000000000000000000000000000000000000..957fc345846acde05345963bcd66eed47b167358
+--- /dev/null
++++ b/batman-adv/patches/0002-batman-adv-invalidate-checksum-on-fragment-reassembl.patch
+@@ -0,0 +1,42 @@
++From 3f5713999a5f61ed7221944276393b4ff40a9416 Mon Sep 17 00:00:00 2001
++Message-Id: <3f5713999a5f61ed7221944276393b4ff40a9416.1516705934.git.mschiffer@universe-factory.net>
++In-Reply-To: <05cee97344804ffb2a8df87603663a098fd0cb36.1516705934.git.mschiffer@universe-factory.net>
++References: <05cee97344804ffb2a8df87603663a098fd0cb36.1516705934.git.mschiffer@universe-factory.net>
++From: Matthias Schiffer <mschiffer@universe-factory.net>
++Date: Tue, 23 Jan 2018 10:24:45 +0100
++Subject: [PATCH 2/2] batman-adv: invalidate checksum on fragment reassembly
++
++A more sophisticated implementation could try to combine fragment checksums
++when all fragments have CHECKSUM_COMPLETE and are split at even offsets.
++For now, we just set ip_summed to CHECKSUM_NONE to avoid "hw csum failure"
++warnings in the kernel log when fragmented frames are received. In
++consequence, skb_pull_rcsum() can be replaced with skb_pull().
++
++Note that in usual setups, packets don't reach batman-adv with
++CHECKSUM_COMPLETE (I assume NICs bail out of checksumming when they see
++batadv's ethtype?), which is why the log messages do nor occur on every
++system using batman-adv. I could reproduce this issue by stacking
++batman-adv on top of a VXLAN interface.
++
++Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
++---
++ net/batman-adv/fragmentation.c | 3 ++-
++ 1 file changed, 2 insertions(+), 1 deletion(-)
++
++diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
++index ebe6e389..1bb2b43f 100644
++--- a/net/batman-adv/fragmentation.c
+++++ b/net/batman-adv/fragmentation.c
++@@ -287,7 +287,8 @@ batadv_frag_merge_packets(struct hlist_head *chain)
++ 	/* Move the existing MAC header to just before the payload. (Override
++ 	 * the fragment header.)
++ 	 */
++-	skb_pull_rcsum(skb_out, hdr_size);
+++	skb_pull(skb_out, hdr_size);
+++	skb_out->ip_summed = CHECKSUM_NONE;
++ 	memmove(skb_out->data - ETH_HLEN, skb_mac_header(skb_out), ETH_HLEN);
++ 	skb_set_mac_header(skb_out, -ETH_HLEN);
++ 	skb_reset_network_header(skb_out);
++-- 
++2.16.1
++