Re: [PATCH net-next v4 2/6] net: qualcomm: rmnet: simplify some byte order logic
From: Alexander Duyck <hidden>
Date: 2021-03-15 16:03:48
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On Mon, Mar 15, 2021 at 6:36 AM Alex Elder [off-list ref] wrote:
quoted hunk ↗ jump to hunk
In rmnet_map_ipv4_ul_csum_header() and rmnet_map_ipv6_ul_csum_header() the offset within a packet at which checksumming should commence is calculated. This calculation involves byte swapping and a forced type conversion that makes it hard to understand. Simplify this by computing the offset in host byte order, then converting the result when assigning it into the header field. Signed-off-by: Alex Elder <redacted> Reviewed-by: Bjorn Andersson <redacted> --- .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 22 ++++++++++--------- 1 file changed, 12 insertions(+), 10 deletions(-)diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c index 21d38167f9618..bd1aa11c9ce59 100644 --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c@@ -197,12 +197,13 @@ 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; + __be16 *hdr = (__be16 *)ul_header; + struct iphdr *ip4h = iphdr; + u16 offset; + + offset = skb_transport_header(skb) - (unsigned char *)iphdr; + ul_header->csum_start_offset = htons(offset);
Rather than using skb_transport_header the correct pointer to use is probably skb_checksum_start. The two are essentially synonymous but the checksumming code is supposed to use skb_checksum_start. Alternatively you could look at possibly using skb_network_header_len as that would be the same value assuming that both headers are the outer headers. Then you could avoid the extra pointer overhead.
quoted hunk ↗ jump to hunk
- 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; if (ip4h->protocol == IPPROTO_UDP)@@ -239,12 +240,13 @@ rmnet_map_ipv6_ul_csum_header(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; + __be16 *hdr = (__be16 *)ul_header; + struct ipv6hdr *ip6h = ip6hdr; + u16 offset; + + offset = skb_transport_header(skb) - (unsigned char *)ip6hdr; + ul_header->csum_start_offset = htons(offset);
Same here.
- 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;
--
2.27.0