1 files changed, 63 insertions, 0 deletions
diff --git a/users/wpcarro/website/blog/posts/tcp-tunneling-note.md b/users/wpcarro/website/blog/posts/tcp-tunneling-note.md
new file mode 100644
index 000000000000..06f6469aff3d
--- /dev/null
+++ b/users/wpcarro/website/blog/posts/tcp-tunneling-note.md
@@ -0,0 +1,63 @@
+## Background
+
+Let's say we'd like to debug a remote machine but use some of the debugging
+tools we have on our local machine like wireshark.
+
+You *can* run `tcpdump` on the remote and then `scp` the file to your local
+machine to analyze the traffic, but after doing that a few times you may want a
+workflow with a tighter feedback loop. For this we'll forward traffic from a
+remote machine to our local machine.
+
+**Note:** There's also `termshark`, which is a `wireshark` TUI that you can run
+on the remote. It's quite cool!
+
+## Local
+
+Run the following on your local machine to forward your remote's traffic:
+
+```shell
+λ ssh -R 4317:127.0.0.1:4317 -N -f user@remote
+```
+
+Here is an abridged explanation of the flags we're passing from `man ssh`:
+
+```
+-N     Do  not  execute  a remote command.  This is useful for just forwarding ports.
+-f     Requests ssh to go to background just before command execution.
+```
+
+**Note:** I couldn't find a good explanation for the `-R` option, so I tried
+removing it and re-running the command, but that results in a resolution error:
+
+```
+ssh: Could not resolve hostname 4317:127.0.0.1:4317: Name or service not known
+```
+
+The remote should now be forwarding traffic from port `4317` to our
+machine.
+
+## Testing
+
+Let's generate some traffic on the remote:
+
+```shell
+λ telnet localhost 4317
+Trying ::1...
+Connected to localhost.
+Escape character is '^]'.
+hello
+world
+```
+
+Locally you should see:
+
+```shell
+λ nc -l 4317 -k # run this *before* running the above command
+hello
+world
+```
+
+You should now be able to `tcpdump -i lo port 4317` or just use `wireshark`
+locally.
+
+Happy debugging!