On 03/10/2023 22.05, Stanislav Fomichev wrote:
When we get a packet on port 9091, we swap src/dst and send it out.
At this point we also request the timestamp and checksum offloads.
Checksum offload is verified by looking at the tcpdump on the other side.
The tool prints pseudo-header csum and the final one it expects.
The final checksum actually matches the incoming packets checksum
because we only flip the src/dst and don't change the payload.
Some other related changes:
- switched to zerocopy mode by default; new flag can be used to force
old behavior
- request fixed tx_metadata_len headroom
- some other small fixes (umem size, fill idx+i, etc)
mvbz3:~# ./xdp_hw_metadata eth3
...
0x1062cb8: rx_desc[0]->addr=80100 addr=80100 comp_addr=80100
rx_hash: 0x2E1B50B9 with RSS type:0x2A
rx_timestamp: 1691436369532047139 (sec:1691436369.5320)
XDP RX-time: 1691436369261756803 (sec:1691436369.2618) delta sec:-0.2703 (-270290.336 usec)
I guess system time isn't configured to be in sync with NIC HW time,
as delta is a negative offset.
AF_XDP time: 1691436369261878839 (sec:1691436369.2619) delta sec:0.0001 (122.036 usec)
The AF_XDP time is also software system time and compared to XDP
RX-time, it shows a delta of 122 usec. This number indicate to me that
the CPU is likely configured with power saving sleep states.
0x1062cb8: ping-pong with csum=3b8e (want de7e) csum_start=54 csum_offset=6
0x1062cb8: complete tx idx=0 addr=10
0x1062cb8: tx_timestamp: 1691436369598419505 (sec:1691436369.5984)
Could we add something that we can relate tx_timestamp to?
Like we do with the other delta calculations, as it helps us to
understand/validate if the number we get back is sane. Like negative
offset aboves tells us that system time sync isn't configured, and that
system have configures C-states.
I suggest delta comparing "tx_timestamp" to "rx_timestamp", as they are
the same clock domain. It will tell us the total time spend from HW RX
to HW TX, counting all the time used by software "ping-pong".
1691436369.5984-1691436369.5320 = 0.0664 sec = 66.4 ms
When implementing this, it could be (1) practical to store the
"rx_timestamp" in the metadata area of the completion packet, or (2)
should we have a mechanism for external storage that can be keyed on the
umem "addr"?
0x1062cb8: complete rx idx=128 addr=80100
mvbz4:~# nc -Nu -q1 ${MVBZ3_LINK_LOCAL_IP}%eth3 9091
mvbz4:~# tcpdump -vvx -i eth3 udp
tcpdump: listening on eth3, link-type EN10MB (Ethernet), snapshot length 262144 bytes
12:26:09.301074 IP6 (flowlabel 0x35fa5, hlim 127, next-header UDP (17) payload length: 11) fe80::1270:fdff:fe48:1087.55807 > fe80::1270:fdff:fe48:1077.9091: [bad udp cksum 0x3b8e -> 0xde7e!] UDP, length 3
0x0000: 6003 5fa5 000b 117f fe80 0000 0000 0000
0x0010: 1270 fdff fe48 1087 fe80 0000 0000 0000
0x0020: 1270 fdff fe48 1077 d9ff 2383 000b 3b8e
0x0030: 7864 70
12:26:09.301976 IP6 (flowlabel 0x35fa5, hlim 127, next-header UDP (17) payload length: 11) fe80::1270:fdff:fe48:1077.9091 > fe80::1270:fdff:fe48:1087.55807: [udp sum ok] UDP, length 3
0x0000: 6003 5fa5 000b 117f fe80 0000 0000 0000
0x0010: 1270 fdff fe48 1077 fe80 0000 0000 0000
0x0020: 1270 fdff fe48 1087 2383 d9ff 000b de7e
0x0030: 7864 70
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
---
tools/testing/selftests/bpf/xdp_hw_metadata.c | 202 +++++++++++++++++-
1 file changed, 192 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 613321eb84c1..ab83d0ba6763 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -10,7 +10,9 @@
* - rx_hash
*
* TX:
- * - TBD
+ * - UDP 9091 packets trigger TX reply
+ * - TX HW timestamp is requested and reported back upon completion
+ * - TX checksum is requested
*/
#include <test_progs.h>
@@ -24,14 +26,17 @@
[...]
@@ -51,22 +56,24 @@ struct xsk *rx_xsk;
[...]
@@ -129,12 +136,22 @@ static void refill_rx(struct xsk *xsk, __u64 addr)
[...]
@@ -228,6 +245,117 @@ static void verify_skb_metadata(int fd)
printf("skb hwtstamp is not found!\n");
}
+static bool complete_tx(struct xsk *xsk)
+{
+ struct xsk_tx_metadata *meta;
+ __u64 addr;
+ void *data;
+ __u32 idx;
+
+ if (!xsk_ring_cons__peek(&xsk->comp, 1, &idx))
+ return false;
+
+ addr = *xsk_ring_cons__comp_addr(&xsk->comp, idx);
+ data = xsk_umem__get_data(xsk->umem_area, addr);
+ meta = data - sizeof(struct xsk_tx_metadata);
+
+ printf("%p: complete tx idx=%u addr=%llx\n", xsk, idx, addr);
+ printf("%p: tx_timestamp: %llu (sec:%0.4f)\n", xsk,
+ meta->completion.tx_timestamp,
+ (double)meta->completion.tx_timestamp / NANOSEC_PER_SEC);
+ xsk_ring_cons__release(&xsk->comp, 1);
+
+ return true;
+}
+
+#define swap(a, b, len) do { \
+ for (int i = 0; i < len; i++) { \
+ __u8 tmp = ((__u8 *)a)[i]; \
+ ((__u8 *)a)[i] = ((__u8 *)b)[i]; \
+ ((__u8 *)b)[i] = tmp; \
+ } \
+} while (0)
+
+static void ping_pong(struct xsk *xsk, void *rx_packet)
+{
+ struct xsk_tx_metadata *meta;
+ struct ipv6hdr *ip6h = NULL;
+ struct iphdr *iph = NULL;
+ struct xdp_desc *tx_desc;
+ struct udphdr *udph;
+ struct ethhdr *eth;
+ __sum16 want_csum;
+ void *data;
+ __u32 idx;
+ int ret;
+ int len;
+
+ ret = xsk_ring_prod__reserve(&xsk->tx, 1, &idx);
+ if (ret != 1) {
+ printf("%p: failed to reserve tx slot\n", xsk);
+ return;
+ }
+
+ tx_desc = xsk_ring_prod__tx_desc(&xsk->tx, idx);
+ tx_desc->addr = idx % (UMEM_NUM / 2) * UMEM_FRAME_SIZE + sizeof(struct xsk_tx_metadata);
+ data = xsk_umem__get_data(xsk->umem_area, tx_desc->addr);
+
+ meta = data - sizeof(struct xsk_tx_metadata);
+ memset(meta, 0, sizeof(*meta));
+ meta->flags = XDP_TX_METADATA_TIMESTAMP;
+
+ eth = rx_packet;
+
+ if (eth->h_proto == htons(ETH_P_IP)) {
+ iph = (void *)(eth + 1);
+ udph = (void *)(iph + 1);
+ } else if (eth->h_proto == htons(ETH_P_IPV6)) {
+ ip6h = (void *)(eth + 1);
+ udph = (void *)(ip6h + 1);
+ } else {
+ printf("%p: failed to detect IP version for ping pong %04x\n", xsk, eth->h_proto);
+ xsk_ring_prod__cancel(&xsk->tx, 1);
+ return;
+ }
+
+ len = ETH_HLEN;
+ if (ip6h)
+ len += sizeof(*ip6h) + ntohs(ip6h->payload_len);
+ if (iph)
+ len += ntohs(iph->tot_len);
+
+ swap(eth->h_dest, eth->h_source, ETH_ALEN);
+ if (iph)
+ swap(&iph->saddr, &iph->daddr, 4);
+ else
+ swap(&ip6h->saddr, &ip6h->daddr, 16);
+ swap(&udph->source, &udph->dest, 2);
+
+ want_csum = udph->check;
+ if (ip6h)
+ udph->check = ~csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
+ ntohs(udph->len), IPPROTO_UDP, 0);
+ else
+ udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
+ ntohs(udph->len), IPPROTO_UDP, 0);
+
+ meta->flags |= XDP_TX_METADATA_CHECKSUM;
+ if (iph)
+ meta->csum_start = sizeof(*eth) + sizeof(*iph);
+ else
+ meta->csum_start = sizeof(*eth) + sizeof(*ip6h);
+ meta->csum_offset = offsetof(struct udphdr, check);
+
+ printf("%p: ping-pong with csum=%04x (want %04x) csum_start=%d csum_offset=%d\n",
+ xsk, ntohs(udph->check), ntohs(want_csum), meta->csum_start, meta->csum_offset);
+
+ memcpy(data, rx_packet, len); /* don't share umem chunk for simplicity */
+ tx_desc->options |= XDP_TX_METADATA;
+ tx_desc->len = len;
+
+ xsk_ring_prod__submit(&xsk->tx, 1);
+}
+
static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t clock_id)
{
const struct xdp_desc *rx_desc;
@@ -250,6 +378,13 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t
while (true) {
errno = 0;
+
+ for (i = 0; i < rxq; i++) {
+ ret = kick_rx(&rx_xsk[i]);
+ if (ret)
+ printf("kick_rx ret=%d\n", ret);
+ }
+
ret = poll(fds, rxq + 1, 1000);
printf("poll: %d (%d) skip=%llu fail=%llu redir=%llu\n",
ret, errno, bpf_obj->bss->pkts_skip,
@@ -280,6 +415,22 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t
xsk, idx, rx_desc->addr, addr, comp_addr);
verify_xdp_metadata(xsk_umem__get_data(xsk->umem_area, addr),
clock_id);
+
+ if (!skip_tx) {
+ /* mirror the packet back */
+ ping_pong(xsk, xsk_umem__get_data(xsk->umem_area, addr));
+
+ ret = kick_tx(xsk);
+ if (ret)
+ printf("kick_tx ret=%d\n", ret);
+
+ for (int j = 0; j < 500; j++) {
+ if (complete_tx(xsk))
+ break;
+ usleep(10*1000);
I don't fully follow why we need this usleep here.
+ }
+ }
+
xsk_ring_cons__release(&xsk->rx, 1);
refill_rx(xsk, comp_addr);
}
@@ -404,21 +555,52 @@ static void timestamping_enable(int fd, int val)
