ieee80211: every MSDU is RFC 1042's, and the bridge-tunnel header is refused

issues/there-is-no-wifi.md

@@ -233,7 +233,7 @@ Depends on: nothing; W6 waits on it.
   - the elements: SSID, rates, DS, TIM, country, RSN, RSNXE, HT, VHT, HE,
     extended capabilities and WMM;
   - A-MSDU;
-  - 802.11 to Ethernet and back (RFC 1042, bridge-tunnel);
+  - 802.11 to Ethernet and back (RFC 1042);
   - the reorder window.
 - **Exit:** host tests of every refusal and hostile length, a malformed
   country element among them; a seeded structured fuzz of a fixed count, as
@@ -242,9 +242,14 @@ Depends on: nothing; W6 waits on it.
   pinned by hash.
 - **Landed** in #924 and #930; the exit is met, the readings checked
   against the text (#924, issuecomment-6173453493).
-- **Owed:** the bridge-tunnel OUI 00-00-F8 and its EtherTypes 0x80F3 and
-  0x8137 checked against ISO/IEC TR 11802-5:1997. Owner: the orchestrator.
-  Exit: checked, and fixed in `lib/ieee80211/src/data.rs` if contradicted.
+- **No bridge-tunnel.** Every MSDU is sent under RFC 1042's header, and one
+  under any other OUI is refused `UnknownOui`, the bridge-tunnel one
+  included: a departure from §5.1.4's recommendation of ISO/IEC TR
+  11802-5:1997's translation. What the selective translation table holds
+  stays unchecked (#924, issuecomment-6173453493, row 62) and nothing
+  depends on it. The decision rests instead on ToyOS's own EtherTypes
+  arriving under RFC 1042, which the capture corpus shows for IPv4 and ARP;
+  it holds no IPv6 or EAPOL frame.
 
 **W2, the handshakes, in `wlan`**, sans-IO: the 4-way and group-key
 handshakes, SAE by hash-to-element, PMF's keys, and the Transition Disable

lib/ieee80211/src/data.rs

@@ -1,7 +1,6 @@
 //! Data frame bodies: the CCMP header (§12.5.2.2), A-MSDU (§9.3.2.2), and translation between an
-//! MSDU and an Ethernet II frame as §5.1.4 recommends, by ISO/IEC TR 11802-5:1997 (formerly IEEE
-//! Std 802.1H): an RFC 1042 LLC/SNAP header, or the bridge-tunnel one for the two EtherTypes its
-//! selective translation table sends that way.
+//! MSDU and an Ethernet II frame under RFC 1042's LLC/SNAP header alone, every EtherType alike:
+//! §5.1.4's bridge-tunnel translation is not implemented, and its OUI is refused as any other.
 
 use crate::frame::Data;
 use crate::read::Reader;
@@ -109,10 +108,6 @@ pub struct Ethernet<'a> {
 }
 
 const SNAP: [u8; 6] = [0xAA, 0xAA, 0x03, 0x00, 0x00, 0x00];
-const BRIDGE_TUNNEL: [u8; 6] = [0xAA, 0xAA, 0x03, 0x00, 0x00, 0xF8];
-/// The EtherTypes the selective translation table carries under the bridge-tunnel OUI: AppleTalk
-/// AARP and IPX.
-const TUNNELED: [u16; 2] = [0x80F3, 0x8137];
 /// The least type: IEEE Std 802.3-2022 §3.2.6 reads a Length/Type value of at most 1500 as a
 /// length and one of at least 1536 (0x0600) as a type.
 const MIN_ETHERTYPE: u16 = 0x0600;
@@ -128,10 +123,7 @@ impl<'a> Ethernet<'a> {
         if [llc0, llc1, llc2] != [0xAA, 0xAA, 0x03] {
             return Err(Refused::NotSnap);
         }
-        if header == SNAP && TUNNELED.contains(&ethertype) {
-            return Err(Refused::TranslatedType);
-        }
-        if header != SNAP && header != BRIDGE_TUNNEL {
+        if header != SNAP {
             return Err(Refused::UnknownOui);
         }
         if ethertype < MIN_ETHERTYPE {
@@ -146,7 +138,7 @@ pub fn llc_snap(ethertype: u16) -> Result<[u8; LLC_SNAP_LEN], Refused> {
     if ethertype < MIN_ETHERTYPE {
         return Err(Refused::LengthField);
     }
-    let [oui0, oui1, oui2, oui3, oui4, oui5] = if TUNNELED.contains(&ethertype) { BRIDGE_TUNNEL } else { SNAP };
+    let [oui0, oui1, oui2, oui3, oui4, oui5] = SNAP;
     let [t0, t1] = ethertype.to_be_bytes();
     Ok([oui0, oui1, oui2, oui3, oui4, oui5, t0, t1])
 }

lib/ieee80211/src/lib.rs

@@ -119,8 +119,7 @@ refusals! {
     SubframePadding = Malformed, "an A-MSDU subframe whose padding runs past the MPDU";
     SnapHeaderAsAddress = Malformed, "an A-MSDU whose first destination is an LLC/SNAP header";
     NotSnap = Unsupported, "an MSDU that is not LLC/SNAP";
-    UnknownOui = Unsupported, "an LLC/SNAP header with an OUI other than RFC 1042's or bridge-tunnel's";
-    TranslatedType = Unsupported, "an RFC 1042 header carrying a type the selective translation table sends by bridge-tunnel";
+    UnknownOui = Unsupported, "an LLC/SNAP header with an OUI other than RFC 1042's";
     LengthField = Unsupported, "a Length/Type value below 0x0600, which IEEE Std 802.3-2022 §3.2.6 does not read as a type";
     ExtendedIvClear = Malformed, "a CCMP header without its Ext IV bit";
     // The reordering buffer, §10.25.6.6.

lib/ieee80211/tests/refusals.rs

@@ -132,7 +132,6 @@ fn cases() -> Vec<(Refused, Refused)> {
         (SnapHeaderAsAddress, amsdu(&[0xAA, 0xAA, 0x03, 0, 0, 0, 0x08, 0x00, 0x45, 0, 0, 0, 0, 0])),
         (NotSnap, ethernet(&[0xF0, 0xF0, 0x03, 0, 0, 0, 0x08, 0x00])),
         (UnknownOui, ethernet(&[0xAA, 0xAA, 0x03, 0x00, 0x10, 0x18, 0x08, 0x00])),
-        (TranslatedType, ethernet(&[0xAA, 0xAA, 0x03, 0, 0, 0, 0x81, 0x37])),
         (LengthField, ethernet(&[0xAA, 0xAA, 0x03, 0, 0, 0, 0x05, 0xFF])),
         (ExtendedIvClear, refusal(CcmpHeader::split(&[1, 0, 0, 0, 0, 0, 0, 0]))),
         (WindowSize, refusal(Window::<u16>::new(Seq::new(0), 257))),
@@ -408,17 +407,18 @@ fn an_rsnxe_ignores_octets_past_its_field() {
 }
 
 #[test]
-fn llc_snap_refuses_a_length_and_tunnels_aarp_and_ipx() {
+fn llc_snap_refuses_a_length_and_is_rfc_1042_for_every_type() {
     assert_eq!(llc_snap(0x05FF), Err(Refused::LengthField));
-    assert_eq!(llc_snap(0x8137).unwrap()[..6], [0xAA, 0xAA, 0x03, 0x00, 0x00, 0xF8]);
-    assert_eq!(llc_snap(0x80F3).unwrap()[..6], [0xAA, 0xAA, 0x03, 0x00, 0x00, 0xF8]);
-    assert_eq!(llc_snap(0x0800).unwrap(), [0xAA, 0xAA, 0x03, 0x00, 0x00, 0x00, 0x08, 0x00]);
+    for ethertype in [0x0800, 0x8137, 0x80F3] {
+        let [t0, t1] = u16::to_be_bytes(ethertype);
+        assert_eq!(llc_snap(ethertype).unwrap(), [0xAA, 0xAA, 0x03, 0x00, 0x00, 0x00, t0, t1]);
+    }
 }
 
 #[test]
-fn a_bridge_tunnel_msdu_is_its_ethertype_on_ethernet() {
-    let eth = Ethernet::from_msdu(Msdu { da: STA, sa: PEER, payload: &[0xAA, 0xAA, 0x03, 0, 0, 0xF8, 0x81, 0x37, 9] }).unwrap();
-    assert_eq!((eth.ethertype, eth.payload), (0x8137, &[9][..]));
+fn a_bridge_tunnel_msdu_is_refused_as_an_unknown_oui() {
+    let msdu = Msdu { da: STA, sa: PEER, payload: &[0xAA, 0xAA, 0x03, 0, 0, 0xF8, 0x81, 0x37, 9] };
+    assert_eq!(Ethernet::from_msdu(msdu), Err(Refused::UnknownOui));
 }
 
 #[test]