• Toke Høiland-Jørgensen's avatar
    fq_codel: generalise ce_threshold marking for subset of traffic · dfcb63ce
    Toke Høiland-Jørgensen authored
    Commit e72aeb9e ("fq_codel: implement L4S style ce_threshold_ect1
    marking") expanded the ce_threshold feature of FQ-CoDel so it can
    be applied to a subset of the traffic, using the ECT(1) bit of the ECN
    field as the classifier. However, hard-coding ECT(1) as the only
    classifier for this feature seems limiting, so let's expand it to be more
    general.
    
    To this end, change the parameter from a ce_threshold_ect1 boolean, to a
    one-byte selector/mask pair (ce_threshold_{selector,mask}) which is applied
    to the whole diffserv/ECN field in the IP header. This makes it possible to
    classify packets by any value in either the ECN field or the diffserv
    field. In particular, setting a selector of INET_ECN_ECT_1 and a mask of
    INET_ECN_MASK corresponds to the functionality before this patch, and a
    mask of ~INET_ECN_MASK allows using the selector as a straight-forward
    match against a diffserv code point:
    
     # apply ce_threshold to ECT(1) traffic
     tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x1/0x3
    
     # apply ce_threshold to ECN-capable traffic marked as diffserv AF22
     tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x50/0xfc
    
    Regardless of the selector chosen, the normal rules for ECN-marking of
    packets still apply, i.e., the flow must still declare itself ECN-capable
    by setting one of the bits in the ECN field to get marked at all.
    
    v2:
    - Add tc usage examples to patch description
    Signed-off-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
    Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
    Link: https://lore.kernel.org/r/20211019174709.69081-1-toke@redhat.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    dfcb63ce
sch_fq_codel.c 19.4 KB