1 files changed, 49 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/sendmsg4_prog.c b/tools/testing/selftests/bpf/progs/sendmsg4_prog.c
new file mode 100644
index 000000000000..a91536b1c47e
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/sendmsg4_prog.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define SRC1_IP4                0xAC100001U /* 172.16.0.1 */
+#define SRC2_IP4                0x00000000U
+#define SRC_REWRITE_IP4         0x7f000004U
+#define DST_IP4                 0xC0A801FEU /* 192.168.1.254 */
+#define DST_REWRITE_IP4         0x7f000001U
+#define DST_PORT                4040
+#define DST_REWRITE_PORT4       4444
+
+int _version SEC("version") = 1;
+
+SEC("cgroup/sendmsg4")
+int sendmsg_v4_prog(struct bpf_sock_addr *ctx)
+{
+        if (ctx->type != SOCK_DGRAM)
+                return 0;
+
+        /* Rewrite source. */
+        if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||
+            ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {
+                ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);
+        } else {
+                /* Unexpected source. Reject sendmsg. */
+                return 0;
+        }
+
+        /* Rewrite destination. */
+        if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
+             ctx->user_port == bpf_htons(DST_PORT)) {
+                ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
+                ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
+        } else {
+                /* Unexpected source. Reject sendmsg. */
+                return 0;
+        }
+
+        return 1;
+}
+
+char _license[] SEC("license") = "GPL";