net: dsa: tag_sja1105: absorb logic for not overwriting precise info into dsa_8021q_rcv()

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>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/20240713211620.1125910-4-paweldembicki@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 71b26ae6db39c6ea801ccc2930917dcff848688e..3cb0293793a594922987595cb07a8bfe737cb7d1 100644 (file)
--- 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 1aba1d05c27a1aa8d387edfc58d668df8dc14cb7..48886d4b7e3e1168e6d85b2b5bbd8c50154121e7 100644 (file)
--- 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);