embryonic connection has been setup and never attempt to abort a tid
before this is done. This fixes a bad race where a listening socket is
closed when the driver is in the middle of step (b) here. The symptom
of this were "ARP miss" errors from the driver followed by tid leaks.
A hardware-offloaded passive open works this way:
a) A SYN "hits" the TCAM entry for a server tid and the chip delivers it
to the queue associated with the server tid (say, queue A). It waits
for a response from the driver telling it what to do.
b) The driver decides it is ok to proceed. It adds the new tid to the
list of embryonic connections associated with the server tid and then
hands off the SYN to the kernel's syncache to make sure that the kernel
okays it too. If it does then the driver provides an L2 table entry,
queue id (say, queue B), etc. and instructs the chip to send the SYN/ACK
response.
c) The chip delivers a status to queue B depending on how the third step
of the 3-way handshake goes. The driver removes the tid from its list
of embryonic connections and either expands the syncache entry or
destroys the tid. In any case all subsequent messages for the new tid
will be delivered to queue B, not queue A. Anything running in queue B
knows that the L2 entry has long been setup and the new flag is of no
interest from here on. If the listener is closed it will deal with
so_comp as normal.
MFC after: 1 week
counter) when the syncache doesn't want the driver to reply to an
incoming SYN. This fixes a harmless bug where tids_in_use would
go out of sync with the hardware counter.
MFC after: 3 days
evicted from the syncache but a later syncache_expand succeeds because
of syncookies. The TOE driver has to resort to more direct means to
install its hooks in the socket in this case.
the TOE driver reports that an active open failed. toe_connect_failed is
supposed to handle this but it should be provided the inpcb instead of the
tcpcb which may no longer be around.
Basically, this is automatic rx zero copy when feasible. TCP payload is
DMA'd directly into the userspace buffer described by the uio submitted
in soreceive by an application.
- Works with sockets that are being handled by the TCP offload engine
of a T4 chip (you need t4_tom.ko module loaded after cxgbe, and an
"ifconfig +toe" on the cxgbe interface).
- Does not require any modification to the application.
- Not enabled by default. Use hw.t4nex.<X>.toe.ddp="1" to enable it.
TCB. Filters are programmed by modifying the TCB too (via a different
routine) and the reply to any TCB update is delivered via a
CPL_SET_TCB_RPL. Figure out whether the reply is for a filter-write or
something else and route it appropriately.
MFC after: 2 weeks
- Stateful TCP offload drivers for Terminator 3 and 4 (T3 and T4) ASICs.
These are available as t3_tom and t4_tom modules that augment cxgb(4)
and cxgbe(4) respectively. The cxgb/cxgbe drivers continue to work as
usual with or without these extra features.
- iWARP driver for Terminator 3 ASIC (kernel verbs). T4 iWARP in the
works and will follow soon.
Build-tested with make universe.
30s overview
============
What interfaces support TCP offload? Look for TOE4 and/or TOE6 in the
capabilities of an interface:
# ifconfig -m | grep TOE
Enable/disable TCP offload on an interface (just like any other ifnet
capability):
# ifconfig cxgbe0 toe
# ifconfig cxgbe0 -toe
Which connections are offloaded? Look for toe4 and/or toe6 in the
output of netstat and sockstat:
# netstat -np tcp | grep toe
# sockstat -46c | grep toe
Reviewed by: bz, gnn
Sponsored by: Chelsio communications.
MFC after: ~3 months (after 9.1, and after ensuring MFC is feasible)
