RE: [PATCH net-next v2 6/6] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum header

Sent: 06 March 2021 03:16

Replace the use of C bit-fields in the rmnet_map_ul_csum_header
structure with a single two-byte (big endian) structure member,
and use field masks to encode or get values within it.

Previously rmnet_map_ipv4_ul_csum_header() would update values in
the host byte-order fields, and then forcibly fix their byte order
using a combination of byte order operations and types.

Instead, just compute the value that needs to go into the new
structure member and save it with a simple byte-order conversion.

Make similar simplifications in rmnet_map_ipv6_ul_csum_header().

Finally, in rmnet_map_checksum_uplink_packet() a set of assignments
zeroes every field in the upload checksum header.  Replace that with
a single memset() operation.

Signed-off-by: Alex Elder <redacted>
Reported-by: kernel test robot <redacted>
---
v2: Fixed to use u16_encode_bits() instead of be16_encode_bits().

 .../ethernet/qualcomm/rmnet/rmnet_map_data.c  | 34 ++++++-------------
 include/linux/if_rmnet.h                      | 21 ++++++------
 2 files changed, 21 insertions(+), 34 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c

b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
index 29d485b868a65..b76ad48da7325 100644

--- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
+++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c

@@ -198,23 +198,19 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr,
 			      struct rmnet_map_ul_csum_header *ul_header,
 			      struct sk_buff *skb)
 {
-	__be16 *hdr = (__be16 *)ul_header;
 	struct iphdr *ip4h = iphdr;
 	u16 offset;
+	u16 val;

 	offset = skb_transport_header(skb) - (unsigned char *)iphdr;
 	ul_header->csum_start_offset = htons(offset);

-	ul_header->csum_insert_offset = skb->csum_offset;
-	ul_header->csum_enabled = 1;
+	val = u16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK);
 	if (ip4h->protocol == IPPROTO_UDP)
-		ul_header->udp_ind = 1;
-	else
-		ul_header->udp_ind = 0;
+		val |= u16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK);
+	val |= u16_encode_bits(skb->csum_offset, MAP_CSUM_UL_OFFSET_FMASK);

-	/* Changing remaining fields to network order */
-	hdr++;
-	*hdr = htons((__force u16)*hdr);
+	ul_header->csum_info = htons(val);