From e49e41b85f51c13fc78138d4881adbbe0b2a0dc4 Mon Sep 17 00:00:00 2001
From: Jordan Potter <me@jordanpotter.com>
Date: Thu, 14 Feb 2019 15:14:17 -0800
Subject: [PATCH] Add troubleshooting instructions for asymmetric routing

---
 README.md | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/README.md b/README.md
index 14a017c..57700ec 100644
--- a/README.md
+++ b/README.md
@@ -21,3 +21,23 @@ docker run -it --rm                                                  \
     --net=container:wireguard                                        \
     appropriate/curl http://httpbin.org/ip
 ```
+
+## Troubleshooting
+
+### Asymmetric Routing
+
+If you see any errors similar to:
+
+```bash
+sysctl: setting key "net.ipv4.conf.all.rp_filter": Read-only file system
+sysctl: setting key "net.ipv4.conf.default.rp_filter": Read-only file system
+```
+
+Then your host is set to discard packets when the route for outbound traffic differs from the route for incoming traffic. To correct this, you'll want to set these values in `/etc/sysctl.conf`:
+
+```bash
+net.ipv4.conf.default.rp_filter = 2
+net.ipv4.conf.all.rp_filter = 2
+```
+
+Afterwards, reboot.