Merge branch 'bpf: devmap: provide rxq after redirect'

Florian Kauer says:

====================
rxq contains a pointer to the device from where
the redirect happened. Currently, the BPF program
that was executed after a redirect via BPF_MAP_TYPE_DEVMAP*
does not have it set.

Add bugfix and related selftest.

---
Changes in v4:
- return -> goto out_close, thanks Toke
- Link to v3: https://lore.kernel.org/r/20240909-devel-koalo-fix-ingress-ifindex-v3-0-66218191ecca@linutronix.de

Changes in v3:
- initialize skel to NULL, thanks Stanislav
- Link to v2: https://lore.kernel.org/r/20240906-devel-koalo-fix-ingress-ifindex-v2-0-4caa12c644b4@linutronix.de

Changes in v2:
- changed fixes tag
- added selftest
- Link to v1: https://lore.kernel.org/r/20240905-devel-koalo-fix-ingress-ifindex-v1-1-d12a0d74c29c@linutronix.de
====================
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/devmap.c

@@ -333,9 +333,11 @@ static int dev_map_hash_get_next_key(struct bpf_map *map, void *key,
 
 static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
 				struct xdp_frame **frames, int n,
-				struct net_device *dev)
+				struct net_device *tx_dev,
+				struct net_device *rx_dev)
 {
-	struct xdp_txq_info txq = { .dev = dev };
+	struct xdp_txq_info txq = { .dev = tx_dev };
+	struct xdp_rxq_info rxq = { .dev = rx_dev };
 	struct xdp_buff xdp;
 	int i, nframes = 0;
 
@@ -346,6 +348,7 @@ static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
 
 		xdp_convert_frame_to_buff(xdpf, &xdp);
 		xdp.txq = &txq;
+		xdp.rxq = &rxq;
 
 		act = bpf_prog_run_xdp(xdp_prog, &xdp);
 		switch (act) {
@@ -360,7 +363,7 @@ static int dev_map_bpf_prog_run(struct bpf_prog *xdp_prog,
 			bpf_warn_invalid_xdp_action(NULL, xdp_prog, act);
 			fallthrough;
 		case XDP_ABORTED:
-			trace_xdp_exception(dev, xdp_prog, act);
+			trace_xdp_exception(tx_dev, xdp_prog, act);
 			fallthrough;
 		case XDP_DROP:
 			xdp_return_frame_rx_napi(xdpf);
@@ -388,7 +391,7 @@ static void bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
 	}
 
 	if (bq->xdp_prog) {
-		to_send = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev);
+		to_send = dev_map_bpf_prog_run(bq->xdp_prog, bq->q, cnt, dev, bq->dev_rx);
 		if (!to_send)
 			goto out;
 	}

tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c

 // SPDX-License-Identifier: GPL-2.0
+#include <arpa/inet.h>
 #include <uapi/linux/bpf.h>
 #include <linux/if_link.h>
+#include <network_helpers.h>
+#include <net/if.h>
 #include <test_progs.h>
 
 #include "test_xdp_devmap_helpers.skel.h"
@@ -8,31 +11,36 @@
 #include "test_xdp_with_devmap_helpers.skel.h"
 
 #define IFINDEX_LO 1
+#define TEST_NS "devmap_attach_ns"
 
 static void test_xdp_with_devmap_helpers(void)
 {
-	struct test_xdp_with_devmap_helpers *skel;
+	struct test_xdp_with_devmap_helpers *skel = NULL;
 	struct bpf_prog_info info = {};
 	struct bpf_devmap_val val = {
 		.ifindex = IFINDEX_LO,
 	};
 	__u32 len = sizeof(info);
-	int err, dm_fd, map_fd;
+	int err, dm_fd, dm_fd_redir, map_fd;
+	struct nstoken *nstoken = NULL;
+	char data[10] = {};
 	__u32 idx = 0;
 
+	SYS(out_close, "ip netns add %s", TEST_NS);
+	nstoken = open_netns(TEST_NS);
+	if (!ASSERT_OK_PTR(nstoken, "open_netns"))
+		goto out_close;
+	SYS(out_close, "ip link set dev lo up");
 
 	skel = test_xdp_with_devmap_helpers__open_and_load();
 	if (!ASSERT_OK_PTR(skel, "test_xdp_with_devmap_helpers__open_and_load"))
-		return;
+		goto out_close;
 
-	dm_fd = bpf_program__fd(skel->progs.xdp_redir_prog);
-	err = bpf_xdp_attach(IFINDEX_LO, dm_fd, XDP_FLAGS_SKB_MODE, NULL);
+	dm_fd_redir = bpf_program__fd(skel->progs.xdp_redir_prog);
+	err = bpf_xdp_attach(IFINDEX_LO, dm_fd_redir, XDP_FLAGS_SKB_MODE, NULL);
 	if (!ASSERT_OK(err, "Generic attach of program with 8-byte devmap"))
 		goto out_close;
 
-	err = bpf_xdp_detach(IFINDEX_LO, XDP_FLAGS_SKB_MODE, NULL);
-	ASSERT_OK(err, "XDP program detach");
-
 	dm_fd = bpf_program__fd(skel->progs.xdp_dummy_dm);
 	map_fd = bpf_map__fd(skel->maps.dm_ports);
 	err = bpf_prog_get_info_by_fd(dm_fd, &info, &len);
@@ -47,6 +55,22 @@ static void test_xdp_with_devmap_helpers(void)
 	ASSERT_OK(err, "Read devmap entry");
 	ASSERT_EQ(info.id, val.bpf_prog.id, "Match program id to devmap entry prog_id");
 
+	/* send a packet to trigger any potential bugs in there */
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
+			    .data_in = &data,
+			    .data_size_in = 10,
+			    .flags = BPF_F_TEST_XDP_LIVE_FRAMES,
+			    .repeat = 1,
+		);
+	err = bpf_prog_test_run_opts(dm_fd_redir, &opts);
+	ASSERT_OK(err, "XDP test run");
+
+	/* wait for the packets to be flushed */
+	kern_sync_rcu();
+
+	err = bpf_xdp_detach(IFINDEX_LO, XDP_FLAGS_SKB_MODE, NULL);
+	ASSERT_OK(err, "XDP program detach");
+
 	/* can not attach BPF_XDP_DEVMAP program to a device */
 	err = bpf_xdp_attach(IFINDEX_LO, dm_fd, XDP_FLAGS_SKB_MODE, NULL);
 	if (!ASSERT_NEQ(err, 0, "Attach of BPF_XDP_DEVMAP program"))
@@ -67,6 +91,8 @@ static void test_xdp_with_devmap_helpers(void)
 	ASSERT_NEQ(err, 0, "Add BPF_XDP program with frags to devmap entry");
 
 out_close:
+	close_netns(nstoken);
+	SYS_NOFAIL("ip netns del %s", TEST_NS);
 	test_xdp_with_devmap_helpers__destroy(skel);
 }
 
@@ -124,6 +150,86 @@ static void test_xdp_with_devmap_frags_helpers(void)
 	test_xdp_with_devmap_frags_helpers__destroy(skel);
 }
 
+static void test_xdp_with_devmap_helpers_veth(void)
+{
+	struct test_xdp_with_devmap_helpers *skel = NULL;
+	struct bpf_prog_info info = {};
+	struct bpf_devmap_val val = {};
+	struct nstoken *nstoken = NULL;
+	__u32 len = sizeof(info);
+	int err, dm_fd, dm_fd_redir, map_fd, ifindex_dst;
+	char data[10] = {};
+	__u32 idx = 0;
+
+	SYS(out_close, "ip netns add %s", TEST_NS);
+	nstoken = open_netns(TEST_NS);
+	if (!ASSERT_OK_PTR(nstoken, "open_netns"))
+		goto out_close;
+
+	SYS(out_close, "ip link add veth_src type veth peer name veth_dst");
+	SYS(out_close, "ip link set dev veth_src up");
+	SYS(out_close, "ip link set dev veth_dst up");
+
+	val.ifindex = if_nametoindex("veth_src");
+	ifindex_dst = if_nametoindex("veth_dst");
+	if (!ASSERT_NEQ(val.ifindex, 0, "val.ifindex") ||
+	    !ASSERT_NEQ(ifindex_dst, 0, "ifindex_dst"))
+		goto out_close;
+
+	skel = test_xdp_with_devmap_helpers__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_xdp_with_devmap_helpers__open_and_load"))
+		goto out_close;
+
+	dm_fd_redir = bpf_program__fd(skel->progs.xdp_redir_prog);
+	err = bpf_xdp_attach(val.ifindex, dm_fd_redir, XDP_FLAGS_DRV_MODE, NULL);
+	if (!ASSERT_OK(err, "Attach of program with 8-byte devmap"))
+		goto out_close;
+
+	dm_fd = bpf_program__fd(skel->progs.xdp_dummy_dm);
+	map_fd = bpf_map__fd(skel->maps.dm_ports);
+	err = bpf_prog_get_info_by_fd(dm_fd, &info, &len);
+	if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd"))
+		goto out_close;
+
+	val.bpf_prog.fd = dm_fd;
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	ASSERT_OK(err, "Add program to devmap entry");
+
+	err = bpf_map_lookup_elem(map_fd, &idx, &val);
+	ASSERT_OK(err, "Read devmap entry");
+	ASSERT_EQ(info.id, val.bpf_prog.id, "Match program id to devmap entry prog_id");
+
+	/* attach dummy to other side to enable reception */
+	dm_fd = bpf_program__fd(skel->progs.xdp_dummy_prog);
+	err = bpf_xdp_attach(ifindex_dst, dm_fd, XDP_FLAGS_DRV_MODE, NULL);
+	if (!ASSERT_OK(err, "Attach of dummy XDP"))
+		goto out_close;
+
+	/* send a packet to trigger any potential bugs in there */
+	DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
+			    .data_in = &data,
+			    .data_size_in = 10,
+			    .flags = BPF_F_TEST_XDP_LIVE_FRAMES,
+			    .repeat = 1,
+		);
+	err = bpf_prog_test_run_opts(dm_fd_redir, &opts);
+	ASSERT_OK(err, "XDP test run");
+
+	/* wait for the packets to be flushed */
+	kern_sync_rcu();
+
+	err = bpf_xdp_detach(val.ifindex, XDP_FLAGS_DRV_MODE, NULL);
+	ASSERT_OK(err, "XDP program detach");
+
+	err = bpf_xdp_detach(ifindex_dst, XDP_FLAGS_DRV_MODE, NULL);
+	ASSERT_OK(err, "XDP program detach");
+
+out_close:
+	close_netns(nstoken);
+	SYS_NOFAIL("ip netns del %s", TEST_NS);
+	test_xdp_with_devmap_helpers__destroy(skel);
+}
+
 void serial_test_xdp_devmap_attach(void)
 {
 	if (test__start_subtest("DEVMAP with programs in entries"))
@@ -134,4 +240,7 @@ void serial_test_xdp_devmap_attach(void)
 
 	if (test__start_subtest("Verifier check of DEVMAP programs"))
 		test_neg_xdp_devmap_helpers();
+
+	if (test__start_subtest("DEVMAP with programs in entries on veth"))
+		test_xdp_with_devmap_helpers_veth();
 }

tools/testing/selftests/bpf/progs/test_xdp_with_devmap_helpers.c

@@ -12,7 +12,7 @@ struct {
 SEC("xdp")
 int xdp_redir_prog(struct xdp_md *ctx)
 {
-	return bpf_redirect_map(&dm_ports, 1, 0);
+	return bpf_redirect_map(&dm_ports, 0, 0);
 }
 
 /* invalid program on DEVMAP entry;