igmp_setup(), which `igmp off` also calls, enabled the lookup of IPv4
multicast in the L2 table. Groups learned while IGMP was on therefore
kept going only to the ports that had reported them, and with reports
no longer trapped nothing updated those entries until a reboot.
The lookup is now enabled in igmp_enable() and disabled in igmp_setup(),
so with IGMP off all IP multicast is flooded again.
Dynamic link aggregation on top of the static LAGG, for RTL8372/8373:
receive, selection and mux state machines (coupled mux, one aggregator
per group), with "lacp show" to look inside. Each of the four trunk
groups runs its own aggregator on the candidate ports assigned with
"lag <n> lacp <ports>"; the engine starts with the first such group and
stops with the last.
LACPDUs reach the CPU through the reserved-multicast trap, so delivery
needs no L2 entry and nothing written per VLAN or per PVID. The trap
acts on the address before the VLAN lookup and before the ingress
filters, so a LACPDU also arrives on a port that admits tagged frames
only and on a port STP holds in blocking, neither of which a forwarded
one reaches. A trapped frame carries no VLAN tag,
so lacp_in() takes the offset of the PDU body from TRAP_RX_BODY(). The
action is set with trap_rma_set(), which leaves the flags sharing that
register alone, and "lacp off" puts the slow-protocols drop default
back. doc/lacp.md and doc/link_aggregation.md record what was measured,
including why the trap looked like a dead end at first.
The web UI gets a Static/LACP mode per group on the LAG page with live
status, and the startup-config validator knows the per-group syntax. A
host-side sandbox for the state machines runs in the test harness
together with the LAG hash check. It drives both forms of an incoming
LACPDU, so the body offset of a trapped one is covered as well.
The L2 table page iterated with the "next unicast" read method, so
static multicast entries such as an IGMP group were invisible. It now
iterates with "next address", skips L3 entries (their layout carries IP
addresses where a MAC is expected), and reports the lowest member of a
multicast entry's port mask, so such an entry shows up as a static
entry on that port.
A port taken out of LACP forgets its partner, so "lacp show" after
"lacp off" no longer reports one. Applying the same candidate set to a
group again, as the LAG page does on every Apply, leaves the trunk
alone instead of tearing it down for a second or two. lacp_in() checks
the frame length and ethertype before reading a LACPDU, so a runt or a
foreign frame on the slow-protocols address cannot leave stale buffer
bytes as a partner. The sandbox covers these three in T20-T22. On the
LAG page, LACP mode with no ports checked sends "lag N lacp off", and
the startup-config validator wants at least one port after "lacp".
Only frames to 01:00:5e:00:00:16 reached the IGMP handler, so v1/v2
reports, which go to the group address, were never seen. The handler
also took the group from the first v3 group record for every type.
Pass all IPv4 multicast to the handler, which takes the IGMP header
from the IP header length, the group from the IGMP header for v1/v2
reports and v2 leaves and from the first group record for v3, and
returns 0 for anything that is not IGMP so it goes on to the IP stack.
The message and record types have names now.
Building with SDCC 4.6.0 emits tons of warnings e.g.:
cmd_parser.c:31: warning 356: object in read-only code space should be const
cmd_parser.c:36: warning 357: pointer to object in read-only code space should be pointer to const
These of course become fatal when building with --Werror.
Comparing resultant binaries, it seems that a single string is shifted
(deduplication?) but the numbers emitted at the end of the build are
otherwise identical.
The RTL tag carries a 4-bit port number for received frames, and the two
places that turn it into a mask bit take the whole byte:
entry.pmask |= (1L << (IGMP_I->rtl_tag.pmask >> 8));
The comment beside it already says only the low four bits count, but nothing
takes them. rtl837x_stp.c:424 does the same extraction and does mask:
stp_scratch = ((uint8_t)HTONS(STP_I->rtl_tag.pmask)) & 0x0f;
With a count above 15 the result is not a bit at all. SDCC narrows the 1L to
16 bits and emits the shift as a djnz loop, so a count of 200 spins the loop
200 times and leaves zero behind: the join adds no port and the leave clears
none, neither saying anything. It also spends those iterations inside packet
handling.
Mask to four bits and shift a uint16_t, which is the width the surrounding
code works in. Six bytes of BANK1.
Worth saying that this does not make snooping work on its own. struct
igmp_pkt has no vlan_tag field while struct eth_in describes the same frame
with one, so every IP and IGMP field below rtl_tag is read four bytes early.
handle_rx() dispatched to igmp_packet_handler() on the destination
address alone, so an ordinary IGMPv3 report off the wire reached the
handler and could write a table entry whether or not anyone had asked
for snooping. The STP branch right above it is gated on stpEnabled;
this brings the IGMP branch in line.
Snooping state lived only in the per-port registers, and the receive
path cannot afford to read one per packet, so the flag shadows it:
igmp_enable() sets it, igmp_setup() clears it, and igmp_setup() runs
from both the boot path and "igmp off".
While here, igmp off becomes an explicit subcommand instead of the
fall-through, and an unrecognised igmp subcommand prints the usage
line rather than silently turning snooping off.
Six bytes of BANK1 and one of xdata, no internal RAM.
igmp_setup() writes the per-port IGMP configuration twice, once with the
value spelled out and once with the same number assembled from the
constants: IGMP_MAX_GROUP | IGMP_PROTOCOL_ENABLE | IGMP_FLOOD is exactly
0x00ff7c15. The second loop carries the comment block explaining the bit
layout, so the literal one is the one to drop.
Today the cost is one redundant register write, because REG_SET is not a
single statement and the unbraced loop body only ever reaches index
machine.max_port + 1. Once the macro is wrapped it becomes one redundant
write per port on every boot and on every "igmp off", which is what makes
this worth removing rather than leaving.
Fifty nine bytes of BANK1 on SWTGW218AS, nothing anywhere else.
SDCC rejects memset() on the generic &entry pointer (error 78,
incompatible types). The ipmc/l2mc table entries are __xdata; pass an
explicit (__xdata uint8_t *) so the call resolves.
This adds an implementation for trapping IGMP packets to the CPU
which will identify IGMPv1/2/3 packets, but handle only v3.
The implementation then inserts/updates/deletes L3 MC entries
in the L3 lookup table. The entries consist of an Ipv4
Destination IP (the IPv4 MC address), a Source IP (0.0.0.0) and
a Portmask. Note that this implementation is not VLAN aware,
as there is no hardware support in the device.
An alternative strategy is to control switching of the L2-MC packets
in which the IPv4-MC packets are transported (dst-MaC is
01:00:5e:xx:yy:zz, with xx:yy:zz corresponding to bits in the Ipv4-MC
address). This will allow to use VLAN-aware packet switching. While
code support is there for table insert/update/deletes, some further
L2 configuration is missing.
There is no support for IPv6 MC, yet.
DrDoof
Matt Merhar
René van Dorst
d00f
bloqaudio
logicog