A reserved-multicast trap goes to the port named in EXT_CPU_CTRL, which
names no port out of reset, so trapped frames were dropped at ingress.
trap_init() points it at the CPU port once at startup, and
trap_rma_set() changes only the action field of an RMA register.
A trapped frame arrives without the VLAN tag a forwarded one gets, so
TRAP_RX_BODY() gives the offset of the payload for both forms.
STP now traps its address while it runs instead of steering it with a
static L2 entry per VLAN, so turning it on no longer walks the VLAN
table and a pvid change no longer needs stp off and on. With STP off
the flooding entries are restored as before.
A trapped BPDU passes the tagged-only ingress filter that drops a
forwarded one, so the stp_setup() warning about such ports goes.
Review asked for this directly: the hardware layout above port_l2mc_set()
would be better as documentation than as a comment, keeping only the two
lines that say what the function does.
doc/l2.md gains a section on static multicast entries, why delivery uses
the forward action rather than the trap, and the SMI layout of the entry.
doc/CpuPort.md gains the layout of the tag's flags and pmask words, with
the byte order trap that cost an afternoon: writing the flags constant raw
instead of through HTONS puts 0x0020 on the wire as 0x2000, which is EFID
rather than LEARN_DIS, and the ASIC then leaves the 0x8899 header on the
frame.
The comments those paragraphs came from are replaced by a pointer to the
file that now holds them.
DrDoof
d00f
air jinkela
logicog