From 31c91503a07f942531da55ac861630bfdf8d00fb Mon Sep 17 00:00:00 2001
From: Matt Corallo <git@bluematt.me>
Date: Tue, 11 May 2021 21:00:12 +0000
Subject: [PATCH] Support a wrapper XDP prog which can call the defined
 xdp_drop meth

---
 install.sh | 25 +++++++++++++++++++++----
 xdp.c      |  2 ++
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/install.sh b/install.sh
index 66ea534..d77a8b0 100755
--- a/install.sh
+++ b/install.sh
@@ -1,11 +1,28 @@
 #!/bin/bash
 set -e
 
+CLANG_ARGS=""
+XDP_SECTION="xdp_drop"
+if [ "$2" != "" ]; then
+	CLANG_ARGS="-DHAVE_WRAPPER"
+	XDP_SECTION="$3"
+	if [ ! -f "$2" -o "$3" = "" ]; then
+		echo "To use a wrapper C file, call as $0 interface path/to/wrapper.c xdp_section wrapper-clang-args"
+		exit 1
+	fi
+fi
+
 RULES="$(birdc show route table flowspec4 primary all)
 $(birdc show route table flowspec6 primary all)"
 
 echo "$RULES" | ./genrules.py --8021q=drop-vlan --v6frag=ignore-parse-if-rule --ihl=parse-options
-clang -g -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -O3 -emit-llvm -c xdp.c -o - | llc -O3 -march=bpf -filetype=obj -o xdp
+clang $CLANG_ARGS -g -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -O3 -emit-llvm -c xdp.c -o xdp.bc
+if [ "$2" != "" ]; then
+	clang $4 -g -std=c99 -pedantic -Wall -Wextra -Wno-pointer-arith -Wno-unused-variable -O3 -emit-llvm -c "$2" -o wrapper.bc
+	llvm-link xdp.bc wrapper.bc | llc -O3 -march=bpf -filetype=obj -o xdp
+else
+	cat xdp.bc | llc -O3 -march=bpf -filetype=obj -o xdp
+fi
 
 echo "Before unload drop count was:"
 ./dropcount.sh || echo "Not loaded"
@@ -13,9 +30,9 @@ echo "Before unload drop count was:"
 ip link set "$1" xdp off
 ip link set "$1" xdpgeneric off
 # Note that sometimes the automated fallback does not work properly so we have to || generic here
-ip link set "$1" xdpoffload obj xdp sec xdp_drop || (
-	echo "Failed to install in NIC, testing in driver..." && ip link set "$1" xdpdrv obj xdp sec xdp_drop || (
-		echo "Failed to install in driver, using generic..." && ip link set "$1" xdpgeneric obj xdp sec xdp_drop
+ip link set "$1" xdpoffload obj xdp sec $XDP_SECTION || (
+	echo "Failed to install in NIC, testing in driver..." && ip link set "$1" xdpdrv obj xdp sec $XDP_SECTION || (
+		echo "Failed to install in driver, using generic..." && ip link set "$1" xdpgeneric obj xdp sec $XDP_SECTION
 	)
 )
 echo "$RULES" | grep "^flow. {" > installed-rules.txt
diff --git a/xdp.c b/xdp.c
index fc8f2c3..b473ace 100644
--- a/xdp.c
+++ b/xdp.c
@@ -186,8 +186,10 @@ struct {
 } rate_map SEC(".maps");
 #endif
 
+#ifndef HAVE_WRAPPER // Set this to call xdp_drop externally
 SEC("xdp_drop")
 #endif
+#endif
 int xdp_drop_prog(struct xdp_md *ctx)
 {
 	const void *const data_end = (void *)(size_t)ctx->data_end;
-- 
2.39.5