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    Subject[PATCH net-next v8 08/16] net: dsa: tag_sja1105: absorb logic for not overwriting precise info into dsa_8021q_rcv()
    Date
    From: Vladimir Oltean <vladimir.oltean@nxp.com>

    In both sja1105_rcv() and sja1110_rcv(), we may have precise source port
    information coming from parallel hardware mechanisms, in addition to the
    tag_8021q header.

    Only sja1105_rcv() has extra logic to not overwrite that precise info
    with what's present in the VLAN tag. This is because sja1110_rcv() gets
    by, by having a reversed set of checks when assigning skb->dev. When the
    source port is imprecise (vbid >=1), source_port and switch_id will be
    set to zeroes by dsa_8021q_rcv(), which might be problematic. But by
    checking for vbid >= 1 first, sja1110_rcv() fends that off.

    We would like to make more code common between sja1105_rcv() and
    sja1110_rcv(), and for that, we need to make sure that sja1110_rcv()
    also goes through the precise source port preservation logic.

    Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
    Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
    ---
    v8, v7, v6:
    - resend only
    v5:
    - add missing SoB
    v4:
    - introduced patch

    net/dsa/tag_8021q.c | 32 +++++++++++++++++++++++++++++---
    net/dsa/tag_sja1105.c | 23 +++--------------------
    2 files changed, 32 insertions(+), 23 deletions(-)

    diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
    index 71b26ae6db39..3cb0293793a5 100644
    --- a/net/dsa/tag_8021q.c
    +++ b/net/dsa/tag_8021q.c
    @@ -497,9 +497,21 @@ struct net_device *dsa_tag_8021q_find_port_by_vbid(struct net_device *conduit,
    }
    EXPORT_SYMBOL_GPL(dsa_tag_8021q_find_port_by_vbid);

    +/**
    + * dsa_8021q_rcv - Decode source information from tag_8021q header
    + * @skb: RX socket buffer
    + * @source_port: pointer to storage for precise source port information.
    + * If this is known already from outside tag_8021q, the pre-initialized
    + * value is preserved. If not known, pass -1.
    + * @switch_id: similar to source_port.
    + * @vbid: pointer to storage for imprecise bridge ID. Must be pre-initialized
    + * with -1. If a positive value is returned, the source_port and switch_id
    + * are invalid.
    + */
    void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id,
    int *vbid)
    {
    + int tmp_source_port, tmp_switch_id, tmp_vbid;
    u16 vid, tci;

    if (skb_vlan_tag_present(skb)) {
    @@ -513,11 +525,25 @@ void dsa_8021q_rcv(struct sk_buff *skb, int *source_port, int *switch_id,

    vid = tci & VLAN_VID_MASK;

    - *source_port = dsa_8021q_rx_source_port(vid);
    - *switch_id = dsa_8021q_rx_switch_id(vid);
    + tmp_source_port = dsa_8021q_rx_source_port(vid);
    + tmp_switch_id = dsa_8021q_rx_switch_id(vid);
    + tmp_vbid = dsa_tag_8021q_rx_vbid(vid);
    +
    + /* Precise source port information is unknown when receiving from a
    + * VLAN-unaware bridging domain, and tmp_source_port and tmp_switch_id
    + * are zeroes in this case.
    + *
    + * Preserve the source information from hardware-specific mechanisms,
    + * if available. This allows us to not overwrite a valid source port
    + * and switch ID with less precise values.
    + */
    + if (tmp_vbid == 0 && *source_port == -1)
    + *source_port = tmp_source_port;
    + if (tmp_vbid == 0 && *switch_id == -1)
    + *switch_id = tmp_switch_id;

    if (vbid)
    - *vbid = dsa_tag_8021q_rx_vbid(vid);
    + *vbid = tmp_vbid;

    skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
    }
    diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
    index 1aba1d05c27a..48886d4b7e3e 100644
    --- a/net/dsa/tag_sja1105.c
    +++ b/net/dsa/tag_sja1105.c
    @@ -524,30 +524,13 @@ static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
    /* Normal data plane traffic and link-local frames are tagged with
    * a tag_8021q VLAN which we have to strip
    */
    - if (sja1105_skb_has_tag_8021q(skb)) {
    - int tmp_source_port = -1, tmp_switch_id = -1;
    -
    - sja1105_vlan_rcv(skb, &tmp_source_port, &tmp_switch_id, &vbid,
    - &vid);
    - /* Preserve the source information from the INCL_SRCPT option,
    - * if available. This allows us to not overwrite a valid source
    - * port and switch ID with zeroes when receiving link-local
    - * frames from a VLAN-unaware bridged port (non-zero vbid) or a
    - * VLAN-aware bridged port (non-zero vid). Furthermore, the
    - * tag_8021q source port information is only of trust when the
    - * vbid is 0 (precise port). Otherwise, tmp_source_port and
    - * tmp_switch_id will be zeroes.
    - */
    - if (vbid == 0 && source_port == -1)
    - source_port = tmp_source_port;
    - if (vbid == 0 && switch_id == -1)
    - switch_id = tmp_switch_id;
    - } else if (source_port == -1 && switch_id == -1) {
    + if (sja1105_skb_has_tag_8021q(skb))
    + sja1105_vlan_rcv(skb, &source_port, &switch_id, &vbid, &vid);
    + else if (source_port == -1 && switch_id == -1)
    /* Packets with no source information have no chance of
    * getting accepted, drop them straight away.
    */
    return NULL;
    - }

    if (source_port != -1 && switch_id != -1)
    skb->dev = dsa_conduit_find_user(netdev, switch_id, source_port);
    --
    2.34.1

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