We'll need to link two objects together to form the fou module.
This means the source can't be called fou, the build system expects
fou.o to be the combined object.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ipv4/Makefile              | 1 +
 net/ipv4/{fou.c => fou_core.c} | 0
 2 files changed, 1 insertion(+)
 rename net/ipv4/{fou.c => fou_core.c} (100%)

diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index bbdd9c44f14e..e694a5e5b030 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_IP_MROUTE) += ipmr.o
 obj-$(CONFIG_IP_MROUTE_COMMON) += ipmr_base.o
 obj-$(CONFIG_NET_IPIP) += ipip.o
 gre-y := gre_demux.o
+fou-y := fou_core.o
 obj-$(CONFIG_NET_FOU) += fou.o
 obj-$(CONFIG_NET_IPGRE_DEMUX) += gre.o
 obj-$(CONFIG_NET_IPGRE) += ip_gre.o

diff --git a/net/ipv4/fou.c b/net/ipv4/fou_core.c
similarity index 100%
rename from net/ipv4/fou.c
rename to net/ipv4/fou_core.c
-- 
2.37.3