selftests: net: do not detect PPPoX loopback

By default, pppd attempts to detect loopbacks on the underlying
interface using a pseudo-randomly generated magic number and checks if
the same value is received. The seed for the PRNG is a hash of hostname
XOR current time XOR pid, which is likely to collide on NIPA, causing
false positives. Disable magic number generation.

Reported-by: Matthieu Baerts <matttbe@kernel.org>
Fixes: 7af2a94f4dcf ("selftests: net: add tests for PPPoL2TP")
Signed-off-by: Qingfang Deng <qingfang.deng@linux.dev>
Link: https://patch.msgid.link/20260603061746.23452-1-qingfang.deng@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/ppp/pppoe-server-options b/tools/testing/selftests/net/ppp/pppoe-server-options
index 66c8c9d319e918c69b1ab0ba603cd5ee23418f8b..cd586be7061bfc280fb38bf28d3cad62302dbc7b 100644 (file)
--- a/tools/testing/selftests/net/ppp/pppoe-server-options
+++ b/tools/testing/selftests/net/ppp/pppoe-server-options
@@ -1,2 +1,3 @@
 noauth
 noipdefault
+nomagic