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Message-ID: <20200903212409.GA14273@ranger.igk.intel.com>
Date: Thu, 3 Sep 2020 23:24:09 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
lorenzo.bianconi@...hat.com, brouer@...hat.com,
echaudro@...hat.com, sameehj@...zon.com, kuba@...nel.org,
john.fastabend@...il.com, daniel@...earbox.net, ast@...nel.org,
shayagr@...zon.com
Subject: Re: [PATCH v2 net-next 7/9] bpf: helpers: add multibuffer support
On Thu, Sep 03, 2020 at 10:58:51PM +0200, Lorenzo Bianconi wrote:
> From: Sameeh Jubran <sameehj@...zon.com>
>
> The implementation is based on this [0] draft by Jesper D. Brouer.
>
> Provided two new helpers:
>
> * bpf_xdp_get_frag_count()
> * bpf_xdp_get_frags_total_size()
>
> [0] xdp mb design - https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
> Signed-off-by: Sameeh Jubran <sameehj@...zon.com>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> include/uapi/linux/bpf.h | 14 ++++++++++++
> net/core/filter.c | 39 ++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 14 ++++++++++++
> 3 files changed, 67 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index c4a6d245619c..53db75095306 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3590,6 +3590,18 @@ union bpf_attr {
> *
> * Return
> * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_xdp_get_frag_count(struct xdp_buff *xdp_md)
> + * Description
> + * Get the total number of frags for a given packet.
> + * Return
> + * The number of frags
> + *
> + * int bpf_xdp_get_frags_total_size(struct xdp_buff *xdp_md)
> + * Description
> + * Get the total size of frags for a given packet.
> + * Return
> + * The total size of frags for a given packet.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3742,6 +3754,8 @@ union bpf_attr {
> FN(d_path), \
> FN(copy_from_user), \
> FN(xdp_adjust_mb_header), \
> + FN(xdp_get_frag_count), \
> + FN(xdp_get_frags_total_size), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> diff --git a/net/core/filter.c b/net/core/filter.c
> index ae6b10cf062d..ba058fc16440 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -3526,6 +3526,41 @@ static const struct bpf_func_proto bpf_xdp_adjust_mb_header_proto = {
> .arg2_type = ARG_ANYTHING,
> };
>
> +BPF_CALL_1(bpf_xdp_get_frag_count, struct xdp_buff*, xdp)
> +{
> + struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> +
> + return xdp->mb ? sinfo->nr_frags : 0;
> +}
> +
> +const struct bpf_func_proto bpf_xdp_get_frag_count_proto = {
> + .func = bpf_xdp_get_frag_count,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_CTX,
> +};
> +
> +BPF_CALL_1(bpf_xdp_get_frags_total_size, struct xdp_buff*, xdp)
> +{
> + struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> + int nfrags, i;
> + int size = 0;
> +
> + nfrags = xdp->mb ? sinfo->nr_frags : 0;
> +
> + for (i = 0; i < nfrags && i < MAX_SKB_FRAGS; i++)
> + size += skb_frag_size(&sinfo->frags[i]);
> +
I only quickly jumped through series and IMHO this helper should be
rewritten/optimized in a way that we bail out as early as possible if
!xdp->mb as the rest of the code on that condition will do nothing and i'm
not sure if compiler would optimize it.
struct skb_shared_info *sinfo;
int nfrags, i;
int size = 0;
if (!xdp->mb)
return 0;
sinfo = xdp_get_shared_info_from_buff(xdp);
nfrags = min(sinfo->nr_frags, MAX_SKB_FRAGS);
for (i = 0; i < nfrags; i++)
size += skb_frag_size(&sinfo->frags[i]);
return size;
Thoughts?
> + return size;
> +}
> +
> +const struct bpf_func_proto bpf_xdp_get_frags_total_size_proto = {
> + .func = bpf_xdp_get_frags_total_size,
> + .gpl_only = false,
> + .ret_type = RET_INTEGER,
> + .arg1_type = ARG_PTR_TO_CTX,
> +};
> +
> BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
> {
> void *data_hard_end = xdp_data_hard_end(xdp); /* use xdp->frame_sz */
> @@ -6889,6 +6924,10 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> return &bpf_xdp_adjust_tail_proto;
> case BPF_FUNC_xdp_adjust_mb_header:
> return &bpf_xdp_adjust_mb_header_proto;
> + case BPF_FUNC_xdp_get_frag_count:
> + return &bpf_xdp_get_frag_count_proto;
> + case BPF_FUNC_xdp_get_frags_total_size:
> + return &bpf_xdp_get_frags_total_size_proto;
> case BPF_FUNC_fib_lookup:
> return &bpf_xdp_fib_lookup_proto;
> #ifdef CONFIG_INET
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 392d52a2ecef..dd4669096cbb 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -3591,6 +3591,18 @@ union bpf_attr {
> *
> * Return
> * 0 on success, or a negative error in case of failure.
> + *
> + * int bpf_xdp_get_frag_count(struct xdp_buff *xdp_md)
> + * Description
> + * Get the total number of frags for a given packet.
> + * Return
> + * The number of frags
> + *
> + * int bpf_xdp_get_frags_total_size(struct xdp_buff *xdp_md)
> + * Description
> + * Get the total size of frags for a given packet.
> + * Return
> + * The total size of frags for a given packet.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3743,6 +3755,8 @@ union bpf_attr {
> FN(d_path), \
> FN(copy_from_user), \
> FN(xdp_adjust_mb_header), \
> + FN(xdp_get_frag_count), \
> + FN(xdp_get_frags_total_size), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> --
> 2.26.2
>
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