exec¶

Pipe messages through an external process.

Synopsis¶

bgpipe [...] -- exec [OPTIONS] COMMAND
bgpipe [...] -- exec -A COMMAND [ARGS...] --

Description¶

The exec stage runs an external command and exchanges BGP messages with it over stdin/stdout. Pipeline messages are serialized (JSON by default) and sent to the command's stdin; the command's stdout is parsed back into messages and injected into the pipeline.

This makes it straightforward to process BGP data with any language - Python, Perl, shell scripts, or compiled programs. The external process receives one message per line and can:

Filter: print only messages it wants to keep
Modify: alter message contents and print the result
Generate: produce new messages on stdout
Drop: simply not print a message to discard it

The command's stderr is forwarded to the bgpipe log.

The stage is both a producer and a consumer, and supports bidirectional operation with -LR.

Use the -A / --args flag to pass arguments to the command. Without -A, only the first argument after exec is treated as the command path. With -A, all arguments up to the next -- are passed to the command.

Options¶

Option	Type	Default	Description
`--keep-stdin`	bool	`false`	Keep running if the command's stdin is closed
`--keep-stdout`	bool	`false`	Keep running if the command's stdout is closed
`--format`	string	`json`	Data format: `json`, `raw`, `mrt`, `exa`, `bmp`, or `obmp`
`--type`	strings		Process only messages of given type(s)
`--skip`	strings		Skip messages of given type(s)
`--read`	bool	`false`	Read-only mode (don't send pipeline output to command)
`--write`	bool	`false`	Write-only mode (don't read command output)
`--copy`	bool	`false`	Mirror messages instead of consuming them
`--pardon`	bool	`false`	Ignore input parsing errors
`--no-seq`	bool	`false`	Overwrite input sequence numbers
`--no-time`	bool	`false`	Overwrite input timestamps
`--no-tags`	bool	`false`	Drop input message tags

Examples¶

Filter updates with a Python script:

bgpipe -o -- read updates.mrt.gz -- exec -A python3 filter.py --

Use sed to rewrite ASNs in OPEN messages:

bgpipe \
    -- connect 192.0.2.1 \
    -- exec -LR -A sed -ure '/"OPEN"/{ s/65055/65001/g }' -- \
    -- connect 10.0.0.1

Process with ExaBGP-compatible scripts:

bgpipe \
    -- listen :179 \
    -- exec --format exa -LR -A /path/to/script.py -- \
    -- connect 192.0.2.1

Write-only: send messages to a monitoring script without reading back:

bgpipe \
    -- connect 192.0.2.1 \
    -- exec --write -LR -A /usr/local/bin/bgp-logger -- \
    -- connect 10.0.0.1

Python Script Example¶

A Python script that filters IPv4 prefixes shorter than /16:

#!/usr/bin/env python3
import sys, json

for line in sys.stdin:
    msg = json.loads(line)
    if msg[3] == "UPDATE":
        if "reach" in msg[4]:
            msg[4]["reach"] = [
                p for p in msg[4]["reach"]
                if int(p.split("/")[1]) < 16
            ]
            if not msg[4]["reach"]:
                continue
    print(json.dumps(msg), flush=True)