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mpmd: Increase UHD-side MTU cap for 10 GbE and 1 GbE

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This gets closer to what our hardware can actually support. See the
comments for further explanations.

This has the side-effect of patching an issue on X410 (using 200 MHz
images) where garbage samples would get injected (one per packet). It
is not, however, the final fix for that problem.
This commit is contained in:
Martin Braun 2021-10-19 18:09:31 +02:00 committed by Aaron Rossetto
parent 2788259ca9
commit a629ce3a46
2 changed files with 18 additions and 8 deletions
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18
host/lib/usrp/mpmd/mpmd_link_if_ctrl_udp.cpp
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@ -29,14 +29,24 @@ using namespace uhd::mpmd::xport;
namespace {
//! Maximum CHDR packet size in bytes
const size_t MPMD_10GE_DATA_FRAME_MAX_SIZE = 7972;
const size_t MPMD_1GE_DATA_FRAME_MAX_SIZE = 1472;
//! Maximum CHDR packet size in bytes.
// Our 10GbE connections use custom FPGA code which caps frames at 8192 bytes.
// However, we artificially limit this to a smaller frame size, which gives us
// a safety margin.
const size_t MPMD_10GE_DATA_FRAME_MAX_SIZE = 8016;
// For 1 GbE, we either go through our on-chip PHY/MAC, which also caps at 8192
// bytes, or we go through the RJ45, and then the DMA to the chip, which can go
// higher. We thus choose the same value as for 10 GbE.
// Note that for 1 GbE, we almost always have an MTU of 1500, so we will rarely
// meet this frame size, but MTU discovery will take care of that. This is just
// a cap to make sure we never try CHDR packets that will clog our fabric.
const size_t MPMD_1GE_DATA_FRAME_MAX_SIZE = 8016;
//! Number of send/recv frames
const size_t MPMD_ETH_NUM_FRAMES = 32;
//!
//! Buffer depth in seconds. We use the link rate to determine how large buffers
// must be to store this many seconds worth of data.
const double MPMD_BUFFER_DEPTH = 20.0e-3; // s
//! For MTU discovery, the time we wait for a packet before calling it
// oversized (seconds).

8
mpm/python/usrp_mpm/discovery.py
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@ -16,9 +16,9 @@ from usrp_mpm.mpmutils import to_binary_str
RESPONSE_PREAMBLE = b"USRP-MPM"
RESPONSE_SEP = b";"
RESPONSE_CLAIMED_KEY = b"claimed"
# "Max MTU" is not a redundant name. We don't know the total path MTU, but we
# can say for sure that it won't exceed a certain value, and that's the max MTU
MAX_MTU = 8000
# A buffer size large enough to capture any UDP packet we receive on the
# discovery socket
MAX_SOCK_BUFSIZ = 9000
# For setsockopt
IP_MTU_DISCOVER = 10
IP_PMTUDISC_DO = 2
@ -71,7 +71,7 @@ def _discovery_process(state, discovery_addr):
try:
while True:
data, sender = sock.recvfrom(MAX_MTU)
data, sender = sock.recvfrom(MAX_SOCK_BUFSIZ)
log.debug("Got poked by: %s", sender[0])
# TODO this is still part of the awful subnet identification
if not sender[0].startswith(discovery_addr_prefix):