bpf, sockmap: Test FIONREAD returns correct bytes in rx buffer with drops

When BPF program drops pkts the sockmap logic 'eats' the packet and
updates copied_seq. In the PASS case where the sk_buff is accepted
we update copied_seq from recvmsg path so we need a new test to
handle the drop case.

Original patch series broke this resulting in

test_sockmap_skb_verdict_fionread:PASS:ioctl(FIONREAD) error 0 nsec
test_sockmap_skb_verdict_fionread:FAIL:ioctl(FIONREAD) unexpected ioctl(FIONREAD): actual 1503041772 != expected 256

After updated patch with fix.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230523025618.113937-14-john.fastabend@gmail.com

1 files changed, 32 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_drop_prog.c b/tools/testing/selftests/bpf/progs/test_sockmap_drop_prog.c
new file mode 100644
index 000000000000..29314805ce42
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sockmap_drop_prog.c
@@ -0,0 +1,32 @@
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 20);
+	__type(key, int);
+	__type(value, int);
+} sock_map_rx SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 20);
+	__type(key, int);
+	__type(value, int);
+} sock_map_tx SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_SOCKMAP);
+	__uint(max_entries, 20);
+	__type(key, int);
+	__type(value, int);
+} sock_map_msg SEC(".maps");
+
+SEC("sk_skb")
+int prog_skb_verdict(struct __sk_buff *skb)
+{
+	return SK_DROP;
+}
+
+char _license[] SEC("license") = "GPL";