On Thu 04 Mar 16:34 CST 2021, Alex Elder wrote:
> 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 <el...@linaro.org>
> ---
> .../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..db76bbf000aa1 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 = be16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK);
Why are you using be16_ here? Won't that cancel the htons() below?
Regards,
Bjorn
> if (ip4h->protocol == IPPROTO_UDP)
> - ul_header->udp_ind = 1;
> - else
> - ul_header->udp_ind = 0;
> + val |= be16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK);
> + val |= be16_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);
>
> skb->ip_summed = CHECKSUM_NONE;
>
> @@ -241,24 +237,19 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr,
> struct rmnet_map_ul_csum_header *ul_header,
> struct sk_buff *skb)
> {
> - __be16 *hdr = (__be16 *)ul_header;
> struct ipv6hdr *ip6h = ip6hdr;
> u16 offset;
> + u16 val;
>
> offset = skb_transport_header(skb) - (unsigned char *)ip6hdr;
> ul_header->csum_start_offset = htons(offset);
>
> - ul_header->csum_insert_offset = skb->csum_offset;
> - ul_header->csum_enabled = 1;
> -
> + val = be16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK);
> if (ip6h->nexthdr == IPPROTO_UDP)
> - ul_header->udp_ind = 1;
> - else
> - ul_header->udp_ind = 0;
> + val |= be16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK);
> + val |= be16_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);
>
> skb->ip_summed = CHECKSUM_NONE;
>
> @@ -425,10 +416,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff
> *skb,
> }
>
> sw_csum:
> - ul_header->csum_start_offset = 0;
> - ul_header->csum_insert_offset = 0;
> - ul_header->csum_enabled = 0;
> - ul_header->udp_ind = 0;
> + memset(ul_header, 0, sizeof(*ul_header));
>
> priv->stats.csum_sw++;
> }
> diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h
> index 1fbb7531238b6..149d696feb520 100644
> --- a/include/linux/if_rmnet.h
> +++ b/include/linux/if_rmnet.h
> @@ -33,17 +33,16 @@ struct rmnet_map_dl_csum_trailer {
>
> struct rmnet_map_ul_csum_header {
> __be16 csum_start_offset;
> -#if defined(__LITTLE_ENDIAN_BITFIELD)
> - u16 csum_insert_offset:14;
> - u16 udp_ind:1;
> - u16 csum_enabled:1;
> -#elif defined (__BIG_ENDIAN_BITFIELD)
> - u16 csum_enabled:1;
> - u16 udp_ind:1;
> - u16 csum_insert_offset:14;
> -#else
> -#error "Please fix <asm/byteorder.h>"
> -#endif
> + __be16 csum_info; /* MAP_CSUM_UL_*_FMASK */
> } __aligned(1);
>
> +/* csum_info field:
> + * ENABLED: 1 = checksum computation requested
> + * UDP: 1 = UDP checksum (zero checkum means no checksum)
> + * OFFSET: where (offset in bytes) to insert computed checksum
> + */
> +#define MAP_CSUM_UL_OFFSET_FMASK GENMASK(13, 0)
> +#define MAP_CSUM_UL_UDP_FMASK GENMASK(14, 14)
> +#define MAP_CSUM_UL_ENABLED_FMASK GENMASK(15, 15)
> +
> #endif /* !(_LINUX_IF_RMNET_H_) */
> --
> 2.20.1
>
