From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 28 Jan 2021 09:18:31 +0000 (+0800)
Subject: net: support ip generic csum processing in skb_csum_hwoffload_help
X-Git-Tag: accepted/tizen/unified/20230118.172025~7901^2~199^2~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=62fafcd63139920eb25b3fbf154177ce3e6f3232;p=platform%2Fkernel%2Flinux-rpi.git

net: support ip generic csum processing in skb_csum_hwoffload_help

NETIF_F_IP|IPV6_CSUM feature flag indicates UDP and TCP csum offload
while NETIF_F_HW_CSUM feature flag indicates ip generic csum offload
for HW, which includes not only for TCP/UDP csum, but also for other
protocols' csum like GRE's.

However, in skb_csum_hwoffload_help() it only checks features against
NETIF_F_CSUM_MASK(NETIF_F_HW|IP|IPV6_CSUM). So if it's a non TCP/UDP
packet and the features doesn't support NETIF_F_HW_CSUM, but supports
NETIF_F_IP|IPV6_CSUM only, it would still return 0 and leave the HW
to do csum.

This patch is to support ip generic csum processing by checking
NETIF_F_HW_CSUM for all protocols, and check (NETIF_F_IP_CSUM |
NETIF_F_IPV6_CSUM) only for TCP and UDP.

Note that we're using skb->csum_offset to check if it's a TCP/UDP
proctol, this might be fragile. However, as Alex said, for now we
only have a few L4 protocols that are requesting Tx csum offload,
we'd better fix this until a new protocol comes with a same csum
offset.

v1->v2:
  - not extend skb->csum_not_inet, but use skb->csum_offset to tell
    if it's an UDP/TCP csum packet.
v2->v3:
  - add a note in the changelog, as Willem suggested.

Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/core/dev.c b/net/core/dev.c
index 6df3f1b..aae116d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3621,7 +3621,18 @@ int skb_csum_hwoffload_help(struct sk_buff *skb,
 		return !!(features & NETIF_F_SCTP_CRC) ? 0 :
 			skb_crc32c_csum_help(skb);
 
-	return !!(features & NETIF_F_CSUM_MASK) ? 0 : skb_checksum_help(skb);
+	if (features & NETIF_F_HW_CSUM)
+		return 0;
+
+	if (features & (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM)) {
+		switch (skb->csum_offset) {
+		case offsetof(struct tcphdr, check):
+		case offsetof(struct udphdr, check):
+			return 0;
+		}
+	}
+
+	return skb_checksum_help(skb);
 }
 EXPORT_SYMBOL(skb_csum_hwoffload_help);