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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/notes.md | 24 | ||||
| -rw-r--r-- | docs/operations.md | 3 | ||||
| -rw-r--r-- | docs/setup.md | 19 |
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diff --git a/docs/notes.md b/docs/notes.md new file mode 100644 index 0000000..d95c6f0 --- /dev/null +++ b/docs/notes.md @@ -0,0 +1,24 @@ +# Notes + +`onion-grab` uses use the default `net.Dial` function, which in turn uses +[goLookupIPCNAMEOrder][] for DNS lookups with the recursive name servers in +`/etc/resolve.conf`. For example, with + + $ cat /etc/resolve.conf + nameserver 8.8.8.8 + nameserver 8.8.4.4 + +[goLookupIPCNAMEOrder]: https://github.com/golang/go/blob/8edcdddb23c6d3f786b465c43b49e8d9a0015082/src/net/dnsclient_unix.go#L595-L804 + +the query will first be directed to `8.8.8.8`; then `8.8.4.4` if no valid answer +is available yet ([lines 663-778][]). If you are running `onion-grab` with +[Mullvad VPN][], specify custom DNS: `mullvad dns set custom 8.8.8.8 8.8.4.4`. + +[lines 663-778]: https://github.com/golang/go/blob/8edcdddb23c6d3f786b465c43b49e8d9a0015082/src/net/dnsclient_unix.go#L663-L778 +[Mullvad VPN]: https://www.mullvad.net/ + +Further, default settings are used to follow at most 10 HTTP 3XX redirects. A +[conservative][] value for the `MaxResponseHeaderBytes` option is 10MiB; the +`onion-grab` default is 16MiB and our measurements bumped this up to 64MiB. + +[conservative]: https://go-review.googlesource.com/c/go/+/21329/2/src/net/http/transport.go diff --git a/docs/operations.md b/docs/operations.md new file mode 100644 index 0000000..1528c32 --- /dev/null +++ b/docs/operations.md @@ -0,0 +1,3 @@ +# Operations + +Placeholder. diff --git a/docs/setup.md b/docs/setup.md new file mode 100644 index 0000000..7e4bdb8 --- /dev/null +++ b/docs/setup.md @@ -0,0 +1,19 @@ +# Setup + +`onion-grab` has been tested on Ubuntu/Debian based systems. If you are running +a large measurement, you may run into issues that are **OS related**. + +## Hints + + - We disabled and stopped `systemd-resolved`, which eventually causes some or + all DNS requests to be blocked when running with many concurrent workers. + - We used Google's `8.8.8.8` and `8.8.4.4`, which [supports 1500qps][] per IP. + - You may need to tinker with `ulimit` and `sysctl`, e.g., if observing that + there are too many open file descriptors or similar. See for example the + value of `ulimit -n` and `sysctl net.ipv4.ip_local_port_range` + +[supports 1500qps]: https://developers.google.com/speed/public-dns/docs/isp + +## Credit + +Björn Töpel helped us debug some of these OS-related issues. |