Subject: [PATCH net] net: qualcomm: rmnet: Fix incorrect UL checksum offload logic

From: Subash Abhinov Kasiviswanathan <[email-masked]>
Date: Thu, 25 Jul 2019 12:07:12 -0600

The udp_ip4_ind bit is set only for IPv4 UDP non-fragmented packets
so that the hardware can flip the checksum to 0xFFFF if the computed
checksum is 0 per RFC768.

However, this bit had to be set for IPv6 UDP non fragmented packets
as well per hardware requirements. Otherwise, IPv6 UDP packets
with computed checksum as 0 were transmitted by hardware and were
dropped in the network.

In addition to setting this bit for IPv6 UDP, the field is also
appropriately renamed to udp_ind as part of this change.

Fixes: 5eb5f8608ef1 ("net: qualcomm: rmnet: Add support for TX checksum offload")
Cc: Sean Tranchetti <[email-masked]>
Signed-off-by: Subash Abhinov Kasiviswanathan <[email-masked]>
---
 drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c | 13 +++++++++----
 include/linux/if_rmnet.h                             |  4 ++--
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 6018992..21d3816 100644
--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
@@ -206,9 +206,9 @@ static void rmnet_map_complement_ipv4_txporthdr_csum_field(void *iphdr)
 	ul_header->csum_insert_offset = skb->csum_offset;
 	ul_header->csum_enabled = 1;
 	if (ip4h->protocol == IPPROTO_UDP)
-		ul_header->udp_ip4_ind = 1;
+		ul_header->udp_ind = 1;
 	else
-		ul_header->udp_ip4_ind = 0;
+		ul_header->udp_ind = 0;
 
 	/* Changing remaining fields to network order */
 	hdr++;
@@ -239,6 +239,7 @@ static void rmnet_map_complement_ipv6_txporthdr_csum_field(void *ip6hdr)
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
+	struct ipv6hdr *ip6h = (struct ipv6hdr *)ip6hdr;
 	__be16 *hdr = (__be16 *)ul_header, offset;
 
 	offset = htons((__force u16)(skb_transport_header(skb) -
@@ -246,7 +247,11 @@ static void rmnet_map_complement_ipv6_txporthdr_csum_field(void *ip6hdr)
 	ul_header->csum_start_offset = offset;
 	ul_header->csum_insert_offset = skb->csum_offset;
 	ul_header->csum_enabled = 1;
-	ul_header->udp_ip4_ind = 0;
+
+	if (ip6h->nexthdr == IPPROTO_UDP)
+		ul_header->udp_ind = 1;
+	else
+		ul_header->udp_ind = 0;
 
 	/* Changing remaining fields to network order */
 	hdr++;
@@ -419,7 +424,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
 	ul_header->csum_start_offset = 0;
 	ul_header->csum_insert_offset = 0;
 	ul_header->csum_enabled = 0;
-	ul_header->udp_ip4_ind = 0;
+	ul_header->udp_ind = 0;
 
 	priv->stats.csum_sw++;
 }
diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
index b4f5403..9661416 100644
--- a/include/linux/if_rmnet.h
+++ b/include/linux/if_rmnet.h
@@ -41,11 +41,11 @@ struct rmnet_map_ul_csum_header {
 	__be16 csum_start_offset;
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	u16 csum_insert_offset:14;
-	u16 udp_ip4_ind:1;
+	u16 udp_ind:1;
 	u16 csum_enabled:1;
 #elif defined (__BIG_ENDIAN_BITFIELD)
 	u16 csum_enabled:1;
-	u16 udp_ip4_ind:1;
+	u16 udp_ind:1;
 	u16 csum_insert_offset:14;
 #else
 #error	"Please fix <asm/byteorder.h>"
-- 
1.9.1