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fix(console): switch conman from ser2net-telnet to direct serial access

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The ser2net layer between conman and the serial devices was causing
stair-stepping in terminal output. conman's dev="host:port" uses telnet
protocol, but ser2net's accepter was raw TCP (no telnet mode). The telnet
NVT state machine in conman was stripping bare CR characters from device
output — particularly from Dell switches that use old-style \n\r (LF+CR)
line endings instead of standard \r\n. In telnet, a bare \r not followed
by \n or NUL is non-compliant and gets dropped, leaving bare \n that
causes stair-stepping in the raw-mode terminal.

Fix: conman now opens serial devices directly via the stable udev
symlinks (/dev/consoles/<name>) with seropts, eliminating the telnet
layer entirely. ser2net is stopped and disabled but remains installed
for emergency TCP access (documented workflow: stop conmand, start
ser2net, use telnet, then reverse).

Architecture change:
  Before: device → serial → ser2net (raw TCP) → conman (telnet NVT) → terminal
  After:  device → serial → conman (direct) → terminal

Verified: 7/7 serial devices held by conmand, 7/7 log files capturing,
all \r bytes preserved in terminal output (confirmed via PTY capture).

💘 Generated with Crush

Assisted-by: Crush:glm-5.2
This commit is contained in:
mrcharles
2026-07-29 18:29:31 -05:00
parent 80693e4f8e
commit fa0c77fb58
6 changed files with 98 additions and 85 deletions
Download Patch File Download Diff File Expand all files Collapse all files
console/setup.sh
+31 -32
View File
@@ -133,35 +133,24 @@ while IFS= read -r line; do
fi
done < "$MAPPING_FILE"
# --- 5. Restart ser2net ---
# --- 5. Stop ser2net (conman owns serial devices directly) ---
echo ""
echo "--- [5/7] Restarting ser2net ---"
systemctl enable ser2net
systemctl restart ser2net
sleep 2
if systemctl is-active --quiet ser2net; then
echo " ser2net is running."
TS_IP=$(tailscale ip -4 2>/dev/null || echo "127.0.0.1")
echo " Listening ports:"
ss -tlnp | grep ser2net | grep -oE "${TS_IP}:[0-9]+" | sort -t: -k2 -n | sed 's/^/ /'
else
echo " WARNING: ser2net failed to start. Checking journal..."
journalctl -u ser2net --no-pager -n 20
fi
echo "--- [5/7] Disabling ser2net ---"
echo " conman now owns serial devices directly. ser2net must NOT run"
echo " simultaneously (only one process can open a serial device at a time)."
systemctl stop ser2net 2>/dev/null || true
systemctl disable ser2net 2>/dev/null || true
echo " ser2net stopped and disabled (available for emergency use)."
# --- 6. Enable + start conmand ---
echo ""
echo "--- [6/7] Starting conmand ---"
# conman package on Debian may not ship a systemd unit. Create one if missing.
if ! systemctl cat conmand >/dev/null 2>&1; then
echo " No systemd unit for conmand — creating one..."
cat > /etc/systemd/system/conmand.service <<'CONMAND_UNIT'
[Unit]
# conman package on Debian may not ship a systemd unit. Create one if missing,
# or update an existing one that still references ser2net.
CONMAND_UNIT_BODY='[Unit]
Description=ConMan (Console Manager)
After=network.target ser2net.service
Requires=ser2net.service
After=network.target
[Service]
Type=forking
@@ -170,10 +159,18 @@ Restart=on-failure
RestartSec=5
[Install]
WantedBy=multi-user.target
CONMAND_UNIT
WantedBy=multi-user.target'
if ! systemctl cat conmand >/dev/null 2>&1; then
echo " No systemd unit for conmand — creating one..."
echo "$CONMAND_UNIT_BODY" > /etc/systemd/system/conmand.service
systemctl daemon-reload
echo " Created /etc/systemd/system/conmand.service"
elif systemctl cat conmand 2>/dev/null | grep -q 'ser2net'; then
echo " conmand unit has ser2net dependency — updating..."
echo "$CONMAND_UNIT_BODY" > /etc/systemd/system/conmand.service
systemctl daemon-reload
echo " Updated /etc/systemd/system/conmand.service (removed ser2net dep)"
fi
# Kill any manually-started conmand first
@@ -200,17 +197,19 @@ fi
echo ""
echo "--- [7/7] Setup complete ---"
echo ""
echo " ser2net TCP ports (connect directly):"
echo " telnet <tailscale-ip> 2001 # pfv-core-sw01"
echo " telnet <tailscale-ip> 2002 # pfv-tor3-mgmt"
echo " ..."
echo " conman owns serial devices directly (no ser2net in the data path)."
echo ""
echo " conman consoles (with logging):"
echo " conman -f pfv-core-sw01"
echo " conman -q # query status"
echo " Connect from any Tailscale workstation:"
echo " conman -d pfv-tsys4:7890 -f pfv-core-sw01"
echo " conman -d pfv-tsys4:7890 -q # list consoles"
echo ""
echo " Emergency direct serial (must stop conmand first):"
echo " systemctl stop conmand"
echo " screen /dev/consoles/pfv-core-sw01"
echo " systemctl start conmand"
echo ""
echo " To regenerate after changing mapping.txt:"
echo " bash generate-config.sh"
echo " udevadm trigger"
echo " systemctl restart ser2net conmand"
echo " systemctl restart conmand"
echo "============================================"