@@ -4,6 +4,19 @@
#define ETH_ALEN 6
#define HDR_SZ (sizeof(struct ethhdr) + sizeof(struct ipv6hdr) + sizeof(struct udphdr))
+
+/**
+ * enum frame_mark - magics to distinguish page/packet paths
+ * @MARK_XMIT: page was recycled due to the frame being "xmitted" by the NIC.
+ * @MARK_IN: frame is being processed by the input XDP prog.
+ * @MARK_SKB: frame did hit the TC ingress hook as an skb.
+ */
+enum frame_mark {
+ MARK_XMIT = 0U,
+ MARK_IN = 0x42,
+ MARK_SKB = 0x45,
+};
+
const volatile int ifindex_out;
const volatile int ifindex_in;
const volatile __u8 expect_dst[ETH_ALEN];
@@ -34,10 +47,10 @@ int xdp_redirect(struct xdp_md *xdp)
if (*metadata != 0x42)
return XDP_ABORTED;
- if (*payload == 0) {
- *payload = 0x42;
+ if (*payload == MARK_XMIT)
pkts_seen_zero++;
- }
+
+ *payload = MARK_IN;
if (bpf_xdp_adjust_meta(xdp, 4))
return XDP_ABORTED;
@@ -51,7 +64,7 @@ int xdp_redirect(struct xdp_md *xdp)
return ret;
}
-static bool check_pkt(void *data, void *data_end)
+static bool check_pkt(void *data, void *data_end, const __u32 mark)
{
struct ipv6hdr *iph = data + sizeof(struct ethhdr);
__u8 *payload = data + HDR_SZ;
@@ -59,13 +72,13 @@ static bool check_pkt(void *data, void *data_end)
if (payload + 1 > data_end)
return false;
- if (iph->nexthdr != IPPROTO_UDP || *payload != 0x42)
+ if (iph->nexthdr != IPPROTO_UDP || *payload != MARK_IN)
return false;
/* reset the payload so the same packet doesn't get counted twice when
* it cycles back through the kernel path and out the dst veth
*/
- *payload = 0;
+ *payload = mark;
return true;
}
@@ -75,11 +88,11 @@ int xdp_count_pkts(struct xdp_md *xdp)
void *data = (void *)(long)xdp->data;
void *data_end = (void *)(long)xdp->data_end;
- if (check_pkt(data, data_end))
+ if (check_pkt(data, data_end, MARK_XMIT))
pkts_seen_xdp++;
- /* Return XDP_DROP to make sure the data page is recycled, like when it
- * exits a physical NIC. Recycled pages will be counted in the
+ /* Return %XDP_DROP to recycle the data page with %MARK_XMIT, like
+ * it exited a physical NIC. Those pages will be counted in the
* pkts_seen_zero counter above.
*/
return XDP_DROP;
@@ -91,9 +104,12 @@ int tc_count_pkts(struct __sk_buff *skb)
void *data = (void *)(long)skb->data;
void *data_end = (void *)(long)skb->data_end;
- if (check_pkt(data, data_end))
+ if (check_pkt(data, data_end, MARK_SKB))
pkts_seen_tc++;
+ /* Will be either recycled or freed, %MARK_SKB makes sure it won't
+ * hit any of the counters above.
+ */
return 0;
}
Currently, the test relies on that only dropped ("xmitted") frames will be recycled and if a frame became an skb, it will be freed later by the stack and never come back to its page_pool. So, it easily gets broken by trying to recycle skbs[0]: test_xdp_do_redirect:PASS:pkt_count_xdp 0 nsec test_xdp_do_redirect:FAIL:pkt_count_zero unexpected pkt_count_zero: actual 9936 != expected 2 test_xdp_do_redirect:PASS:pkt_count_tc 0 nsec That huge mismatch happened because after the TC ingress hook zeroes the magic, the page gets recycled when skb is freed, not returned to the MM layer. "Live frames" mode initializes only new pages and keeps the recycled ones as is by design, so they appear with zeroed magic on the Rx path again. Expand the possible magic values from two: 0 (was "xmitted"/dropped or did hit the TC hook) and 0x42 (hit the input XDP prog) to three: the new one will mark frames hit the TC hook, so that they will elide both @pkt_count_zero and @pkt_count_xdp. They can then be recycled to their page_pool or returned to the page allocator, this won't affect the counters anyhow. Just make sure to mark them as "input" (0x42) when they appear on the Rx path again. Also make an enum from those magics, so that they will be always visible and can be changed in just one place anytime. This also eases adding any new marks later on. Link: https://github.com/kernel-patches/bpf/actions/runs/4386538411/jobs/7681081789 Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com> --- .../bpf/progs/test_xdp_do_redirect.c | 36 +++++++++++++------ 1 file changed, 26 insertions(+), 10 deletions(-)