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Date: Mon, 20 May 2019 08:49:26 -0700
From: Bjorn Andersson <bjorn.andersson@...aro.org>
To: Alex Elder <elder@...aro.org>
Cc: arnd@...db.de, subashab@...eaurora.org, david.brown@...aro.org,
agross@...nel.org, davem@...emloft.net,
ilias.apalodimas@...aro.org, cpratapa@...eaurora.org,
syadagir@...eaurora.org, evgreen@...omium.org, benchan@...gle.com,
ejcaruso@...gle.com, netdev@...r.kernel.org,
linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] net: qualcomm: rmnet: don't use C bit-fields in
rmnet checksum header
On Mon 20 May 06:53 PDT 2019, Alex Elder wrote:
> Replace the use of C bit-fields in the rmnet_map_ul_csum_header
> structure with a single integral structure member, and use field
> masks to encode or get values within that member.
>
> Note that the previous C bit-fields were defined with CPU local
> endianness. Their values were computed and then forecfully converted
> to network byte order in rmnet_map_ipv4_ul_csum_header(). Simplify
> that function, and properly define the new csum_info member as a big
> endian value.
>
> Make similar simplifications in rmnet_map_ipv6_ul_csum_header().
>
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> Signed-off-by: Alex Elder <elder@...aro.org>
> ---
> .../net/ethernet/qualcomm/rmnet/rmnet_map.h | 9 ++--
> .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 50 ++++++++-----------
> 2 files changed, 26 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> index a56209645c81..f3231c26badd 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map.h
> @@ -60,11 +60,14 @@ struct rmnet_map_dl_csum_trailer {
>
> struct rmnet_map_ul_csum_header {
> __be16 csum_start_offset;
> - u16 csum_insert_offset:14;
> - u16 udp_ip4_ind:1;
> - u16 csum_enabled:1;
> + __be16 csum_info; /* RMNET_MAP_UL_* */
> } __aligned(1);
>
> +/* NOTE: These field masks are defined in CPU byte order */
> +#define RMNET_MAP_UL_CSUM_INSERT_FMASK GENMASK(13, 0)
> +#define RMNET_MAP_UL_CSUM_UDP_FMASK GENMASK(14, 14) /* 0: IP; 1: UDP */
> +#define RMNET_MAP_UL_CSUM_ENABLED_FMASK GENMASK(15, 15)
> +
> #define RMNET_MAP_COMMAND_REQUEST 0
> #define RMNET_MAP_COMMAND_ACK 1
> #define RMNET_MAP_COMMAND_UNSUPPORTED 2
> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> index 10d2d582a9ce..72b64114505a 100644
> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c
> @@ -207,22 +207,18 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr,
> struct rmnet_map_ul_csum_header *ul_header,
> struct sk_buff *skb)
> {
> - struct iphdr *ip4h = (struct iphdr *)iphdr;
> - __be16 *hdr = (__be16 *)ul_header, offset;
> + struct iphdr *ip4h = iphdr;
> + u16 offset;
> + u16 val;
>
> - offset = htons((__force u16)(skb_transport_header(skb) -
> - (unsigned char *)iphdr));
> - ul_header->csum_start_offset = offset;
> - ul_header->csum_insert_offset = skb->csum_offset;
> - ul_header->csum_enabled = 1;
> + offset = skb_transport_header(skb) - (unsigned char *)iphdr;
> + ul_header->csum_start_offset = htons(offset);
> +
> + val = u16_encode_bits(skb->csum_offset, RMNET_MAP_UL_CSUM_INSERT_FMASK);
> + val |= RMNET_MAP_UL_CSUM_ENABLED_FMASK;
> if (ip4h->protocol == IPPROTO_UDP)
> - ul_header->udp_ip4_ind = 1;
> - else
> - ul_header->udp_ip4_ind = 0;
> -
> - /* Changing remaining fields to network order */
> - hdr++;
> - *hdr = htons((__force u16)*hdr);
> + val |= RMNET_MAP_UL_CSUM_UDP_FMASK;
> + ul_header->csum_info = htons(val);
>
> skb->ip_summed = CHECKSUM_NONE;
>
> @@ -249,18 +245,16 @@ 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, offset;
> + u16 offset;
> + u16 val;
>
> - offset = htons((__force u16)(skb_transport_header(skb) -
> - (unsigned char *)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;
> + offset = skb_transport_header(skb) - (unsigned char *)ip6hdr;
> + ul_header->csum_start_offset = htons(offset);
>
> - /* Changing remaining fields to network order */
> - hdr++;
> - *hdr = htons((__force u16)*hdr);
> + val = u16_encode_bits(skb->csum_offset, RMNET_MAP_UL_CSUM_INSERT_FMASK);
> + val |= RMNET_MAP_UL_CSUM_ENABLED_FMASK;
> + /* Not UDP, so that field is 0 */
> + ul_header->csum_info = htons(val);
>
> skb->ip_summed = CHECKSUM_NONE;
>
> @@ -400,8 +394,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff *skb,
> struct rmnet_map_ul_csum_header *ul_header;
> void *iphdr;
>
> - ul_header = (struct rmnet_map_ul_csum_header *)
> - skb_push(skb, sizeof(struct rmnet_map_ul_csum_header));
> + ul_header = skb_push(skb, sizeof(*ul_header));
>
> if (unlikely(!(orig_dev->features &
> (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM))))
> @@ -428,10 +421,7 @@ 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_ip4_ind = 0;
> + memset(ul_header, 0, sizeof(*ul_header));
>
> priv->stats.csum_sw++;
> }
> --
> 2.20.1
>
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