The TODO next to the disabled TCP checksum code asks which bit of the RX tag
carries the result. It is bit 2 of byte 1: the hardware sets it when the L4
checksum is bad.
That answers the question for UDP as well, which was not being checked either
because UIP_CONF_UDP_CHECKSUMS is 0. Both paths now read the flag instead of
running a checksum over the payload on the 8051.
A zero UDP checksum, which is optional in IPv4, is not flagged by the hardware,
so DHCP keeps working and no extra condition is needed.
rx_headers lives in rtlplayground.c, which the host tests do not link, so
test_httpd_tx carries the storage itself the way it already carries uip_buf.
A zeroed descriptor reads as a good checksum, so the existing scenarios are
unaffected.
A new scenario sets the flag on a request and expects it counted as a checksum
error and left unanswered, then sends the same request with the flag clear and
expects it served. Built against uip.c without this change, those first two
checks fail and the two control checks still pass, so the scenario tells the
two versions apart rather than merely exercising the code.
Costs 156 bytes of code on SWTGW218AS and no extra XDATA.
IPBUF is laid out for frames we send, with the 12 byte TX descriptor in
front of the Ethernet header. A received frame starts with the Ethernet
header at uip_buf[0] and carries the RTL and VLAN tags after the
addresses, so IPBUF->ethhdr.src read the port mask and both VLAN fields
as a MAC. Every IP packet from the local network then replaced the
sender's ARP entry with that, and our replies went to an address nobody
has. The IP source address sits at the same offset in both layouts,
which is why the rest looked right.
Use BUF, the receive view uip_arp_arpin() already works from.
uip_arp_ipin() is an empty macro with its body under #if 0, both inherited
from the uIP import and untouched since. That leaves uip_arp_update()
reachable only from uip_arp_arpin(), so an entry is refreshed only by ARP
addressed to us and ages out after UIP_ARP_MAXAGE no matter how much traffic
passed over it.
When it goes, the next transmission to that host hits the miss path of
uip_arp_out(), which overwrites the packet in uip_buf with an ARP request and
returns. For TCP that costs a retransmission. For UDP nothing retransmits, and
handle_tx() sends the UDP connections through uip_arp_out() too, so the
datagram is lost.
The body could not be enabled as written: uip_len -= sizeof(struct uip_eth_hdr)
is a leftover from when UIP_LLH_LEN was 0. Here it is ETHER_HEADER_SIZE +
RTL_FRAME_DESC_SIZE and uip.c reads the IP header at uip_buf[UIP_LLH_LEN], so
uip_len has to keep the link layer in it. The rest of the function is sound.
* uip: time out an ESTABLISHED connection whose peer went silent
uIP has no keepalive and no idle timeout for an ESTABLISHED connection, so
a peer that vanishes without FIN or RST holds it open forever. A crashed
client does it, and so does a SYN caught while the switch is still
booting. With UIP_CONF_MAX_CONNECTIONS = 1 that wedges the single slot:
the web UI stops answering, port 80 no longer even SYN-ACKs, and only a
power cycle recovers it. Every other TCP state already has an exit path
(UIP_MAXRTX, UIP_TIME_WAIT_TIMEOUT); idle ESTABLISHED was the one hole.
Close it inside uIP rather than in httpd, so any future TCP service is
covered too. The retransmission timer is unused while nothing is in
flight, so the idle count lives in it: a 1 Hz strobe derived from the
uip_periodic() rate ages it, any arriving segment clears it, and past the
limit the connection is aborted through the same path as UIP_MAXRTX. Two
new options in uipopt.h, default off; this project enables 30 s.
httpd also joins uip_timedout() to its cleanup: it only handled closed
and aborted, so both this timeout and the existing UIP_MAXRTX one would
have left the transfer state stuck on a dead connection.
* uip: keep the tuning values out of the prose
The comment named the timeout and the tick rate, which go stale the
moment either constant is edited. It now says why an idle connection
is aged out and leaves the numbers to the defines under it.
* uip: parenthesise UIP_LLH_LEN
The macro expands to a bare sum, so wherever it is subtracted the second term
gets added instead. UIP_TCP_MSS - and with it UIP_RECEIVE_WINDOW - therefore
comes out 24 bytes above the buffer's real capacity. UIP_APPDATA_SIZE and
UIP_REASS_BUFSIZE are wrong the same way, though neither is reachable today.
The additions, uip_buf[UIP_LLH_LEN] and friends, were right by luck.
* uip: keep the advertised MSS below the buffer edge
Deriving the MSS straight from the buffer size makes the switch advertise
exactly the segment that fills uip_buf to its last byte, and a peer that takes
it literally corrupts every large upload: the firmware image arrives fully
acknowledged, with no retransmissions on the wire, yet the CRC over the
streamed body never matches and the flash write is abandoned.
Isolated by changing nothing but the segment size, same buffer and same file:
1490-byte segments fail four times out of four, 1460-byte segments succeed,
745-byte segments succeed. Linux halves its segments against a window this
small, so only macOS on a jumbo link ever produces a full-size segment - which
is why the failure hides so well.
Where exactly the full segment breaks the stream is not pinned down yet; until
it is, the advertised MSS stays a step below the edge.
* uip: size the buffer to the largest frame the CPU port accepts
UIP_TCP_MSS derives from UIP_CONF_BUFFER_SIZE, and the buffer was large enough
for frames the hardware will never deliver, so the switch advertised a segment
size no peer could usefully reach. A client on a jumbo-MTU link took it at its
word and the oversized replies went nowhere.
Size the buffer to the ingress limit instead. ICMP bypasses MSS and so probes
the hardware directly: on a SWTGW218AS a 1502-byte payload is answered and 1503
never arrives, which puts the largest frame the NIC hands us at 1556 bytes of
uip_buf. UIP_TCP_MSS then derives to 1490, the same edge measured over TCP.
Frames above the limit are dropped by the NIC rather than written to the
buffer - an 8 kB ping leaves the switch untouched - so nothing overruns it.
Frees 644 bytes of XDATA.
* uip: trim these comments, one of which had stopped being true
The note above UIP_CONF_BUFFER_SIZE claimed the MSS derives from it as 1490.
It does not: the commit that follows pins the MSS at 1460 on purpose, a step
below that ceiling, because a segment filling the buffer to its last byte
corrupts large uploads. Left as it was, the file argued with itself.
Both blocks are shorter now. What justifies the numbers stays, which is the
ICMP measurement behind 1556 and the four-out-of-four failure behind 1460.
What went is the storytelling around them, which belongs in this thread rather
than in a config header.
* uip: derive the MSS from the buffer again, minus explicit headroom
The review asked why the buffer size and the MSS are both set by hand when one
used to follow from the other. They answer different questions, but the gap
between them is a number in its own right, so it gets a name now:
UIP_CONF_BUFFER_EXTRA, and UIP_TCP_MSS goes back to being derived.
The headroom is where the measurement lives. A segment that fills uip_buf to
its last byte corrupts large uploads: with nothing but the segment size
changing, 1490 fails four times out of four and 1460 succeeds. With the buffer
sized to the frame the NIC accepts, an extra of 30 lands on 1460.
Deriving it the other way round does not work. Sizing the buffer from a 1460
byte MSS gives 1526, which is 30 bytes under the frame the NIC actually
delivers. A 1502 byte ICMP payload occupies 1556 bytes of uip_buf and is
answered today, and it would stop fitting.
The generated image is byte for byte the same as the one with 1460 written out,
so the expression lands on the value that was measured.
---------
Co-authored-by: d00f <tokyusho@chatik.pl>
We use the SoC's UUID to generate a fixed MAC for a particular
switch device. The MAC generated uses a Realtek prefix and then
is followed by 3 bytes genertaed from the first 3 bytes of the
UUID xored with the last byte in order to prevent being able
to deduce the UUID from the public MAC.
RTL has up to 3 SCL pins and up to 4 SDA pins. Lets allow configuring
I2C with individual BUS numbers instead of 0/1 I2C.
This enables support for devices where SCL line is not shared between
SFP modules. MUX registry is now initialized depending on needed
pin function.
More over, some SFP pins require special MUX settings, lets initialize
those depending on SFP configuration. This adds TX Disable pin,
which right now is set to low at startup.
Caveats:
- We may still override MUX registry later
- Not sure how to handle invalid bus definitions
- Without SFP is it fine to *not* initialize anything?
- Do to RAM limitation we do inititalize output GPIO to low
d00f
René van Dorst
logicog
bennydiamond
feelfree69
logicog
feelfree69
diijkstra