Propagate DPDK mbuf RX timestamp to FreeBSD mbuf rcv_tstmp

Enable RTE_ETH_RX_OFFLOAD_TIMESTAMP on ports where the NIC supports it,
register the timestamp dynamic field and flag via
rte_mbuf_dyn_rx_timestamp_register() after rte_eth_dev_start() (when
the PMD has registered the dynfield), and copy it into the FreeBSD
mbuf's m_pkthdr.rcv_tstmp so that the existing SO_TIMESTAMP /
SCM_TIMESTAMP path delivers it to userspace.

Uses the DPDK 23.11 dynamic field API: checks the registered dynflag
mask per-packet (not the legacy RTE_MBUF_F_RX_IEEE1588_TMST) and reads
the timestamp via RTE_MBUF_DYNFIELD at the registered offset.

When HW timestamps are not available the offload is not enabled, the
dynflag is never set, and the new code path is never entered — fully
backward compatible.

Fixes: #1045

Author: tarun-t

lib/ff_dpdk_if.c

@@ -54,6 +54,7 @@
 #include <rte_udp.h>
 #include <rte_eth_bond.h>
 #include <rte_eth_bond_8023ad.h>
+#include <rte_mbuf_dyn.h>
 
 #include "ff_dpdk_if.h"
 #include "ff_dpdk_pcap.h"
@@ -80,6 +81,8 @@ static int numa_on;
 
 static unsigned idle_sleep;
 static unsigned pkt_tx_delay;
+static int timestamp_dynfield_offset = -1;
+static uint64_t timestamp_dynflag_mask;
 static uint64_t usr_cb_tsc;
 static int stop_loop;
 
@@ -740,6 +743,11 @@ init_port_start(void)
                     pconf->hw_features.rx_csum = 1;
                 }
 
+                if (dev_info.rx_offload_capa & RTE_ETH_RX_OFFLOAD_TIMESTAMP) {
+                    ff_log(FF_LOG_INFO, FF_LOGTYPE_FSTACK_LIB, "RX timestamp offload supported\n");
+                    port_conf.rxmode.offloads |= RTE_ETH_RX_OFFLOAD_TIMESTAMP;
+                }
+
                 if (ff_global_cfg.dpdk.tx_csum_offoad_skip == 0) {
                     if ((dev_info.tx_offload_capa & RTE_ETH_TX_OFFLOAD_IPV4_CKSUM)) {
                         ff_log(FF_LOG_INFO, FF_LOGTYPE_FSTACK_LIB, "TX ip checksum offload supported\n");
@@ -851,6 +859,20 @@ init_port_start(void)
                 return ret;
             }
 
+            if ((port_conf.rxmode.offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP) &&
+                timestamp_dynfield_offset < 0) {
+                ret = rte_mbuf_dyn_rx_timestamp_register(
+                    &timestamp_dynfield_offset, &timestamp_dynflag_mask);
+                if (ret == 0) {
+                    ff_log(FF_LOG_INFO, FF_LOGTYPE_FSTACK_LIB,
+                        "RX timestamp dynfield registered, offset=%d\n",
+                        timestamp_dynfield_offset);
+                } else {
+                    ff_log(FF_LOG_ERR, FF_LOGTYPE_FSTACK_LIB,
+                        "RX timestamp dynfield registration failed\n");
+                }
+            }
+
 //RSS reta update will failed when enable flow isolate
 #if !defined(FF_FLOW_ISOLATE) && !defined(FF_FLOW_IPIP)
             if (nb_queues > 1) {
@@ -1459,6 +1481,13 @@ ff_veth_input(const struct ff_dpdk_if_context *ctx, struct rte_mbuf *pkt)
         ff_mbuf_set_vlan_info(hdr, pkt->vlan_tci);
     }
 
+    if ((pkt->ol_flags & timestamp_dynflag_mask) &&
+        timestamp_dynfield_offset >= 0) {
+        rte_mbuf_timestamp_t ts = *RTE_MBUF_DYNFIELD(
+            pkt, timestamp_dynfield_offset, rte_mbuf_timestamp_t *);
+        ff_mbuf_set_timestamp(hdr, (uint64_t)ts);
+    }
+
     struct rte_mbuf *pn = pkt->next;
     void *prev = hdr;
     while(pn != NULL) {

lib/ff_veth.c

@@ -1124,3 +1124,10 @@ ff_mbuf_set_vlan_info(void *hdr, uint16_t vlan_tci) {
     return;
 }
 
+void
+ff_mbuf_set_timestamp(void *hdr, uint64_t timestamp) {
+    struct mbuf *m = (struct mbuf *)hdr;
+    m->m_pkthdr.rcv_tstmp = timestamp;
+    m->m_flags |= M_TSTMP | M_TSTMP_HPREC;
+}
+

lib/ff_veth.h

@@ -52,5 +52,6 @@ void *ff_veth_get_softc(void *host_ctx);
 void ff_veth_free_softc(void *softc);
 
 void ff_mbuf_set_vlan_info(void *hdr, uint16_t vlan_tci);
+void ff_mbuf_set_timestamp(void *hdr, uint64_t timestamp);
 
 #endif /* ifndef _FSTACK_VETH_H */