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[34.48.4.250]) by smtp.gmail.com with ESMTPSA id 00721157ae682-81f657a14d9sm23339467b3.13.2026.07.26.13.29.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Jul 2026 13:29:15 -0700 (PDT) From: Willem de Bruijn To: netdev@vger.kernel.org Cc: davem@davemloft.net, kuba@kernel.org, edumazet@google.com, pabeni@redhat.com, horms@kernel.org, andrew@lunn.ch, mohsin.bashr@gmail.com, Willem de Bruijn Subject: [PATCH net-next v3 7/7] net: pktgen: add support for SO_TXTIME Date: Sun, 26 Jul 2026 16:28:51 -0400 Message-ID: <20260726202902.760552-8-willemdebruijn.kernel@gmail.com> X-Mailer: git-send-email 2.55.0.229.g6434b31f56-goog In-Reply-To: <20260726202902.760552-1-willemdebruijn.kernel@gmail.com> References: <20260726202902.760552-1-willemdebruijn.kernel@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Willem de Bruijn Introduce support for setting the SO_TXTIME delivery txtime on generated packets. This allows testing pacing and scheduling features in the network stack (e.g., sch_fq, sch_taprio) and drivers. Add a new flag 'TXTIME' to enable this feature. Add two new configuration parameters: - txtime_delay: offset from now in ns - txtime_clockid: clock to use (monotonic, realtime, tai) The queue_xmit mode can clear skb->tstamp in-flight, so this must be used without clone_skb. Signed-off-by: Willem de Bruijn --- Sashiko: ignore data races in the control fields. Pktgen requires superuser privileges, has many such races already, which are benign. Changes v1 -> v2 - avoid data race on txtime_delay - same on flags - (minor) style: avoid two >80 column warnings (checkpatch) v1: https://lore.kernel.org/netdev/20260706133433.3142805-8-willemdebruijn.kernel@gmail.com/ fixup pktgen: txtime_delay READ_ONCE --- net/core/pktgen.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 92 insertions(+), 1 deletion(-) diff --git a/net/core/pktgen.c b/net/core/pktgen.c index 5b4dd04d6124..7897e4220513 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -201,6 +201,7 @@ pf(SVID_RND) /* Random SVLAN ID */ \ pf(NODE) /* Node memory alloc*/ \ pf(SHARED) /* Shared SKB */ \ + pf(TXTIME) /* SO_TXTIME support */ \ #define pf(flag) flag##_SHIFT, enum pkt_flags { @@ -291,6 +292,10 @@ struct pktgen_dev { struct page *page; u64 delay; /* nano-seconds */ + /* TXTIME support */ + u64 txtime_delay; /* transmit time delay in ns */ + clockid_t txtime_clockid; /* clockid for SO_TXTIME */ + __u64 count; /* Default No packets to send */ __u64 sofar; /* How many pkts we've sent so far */ __u64 tx_bytes; /* How many bytes we've transmitted */ @@ -666,6 +671,17 @@ static int pktgen_if_show(struct seq_file *seq, void *v) if (pkt_dev->node >= 0) seq_printf(seq, " node: %d\n", pkt_dev->node); + if (pkt_dev->flags & F_TXTIME) { + clockid_t clockid = READ_ONCE(pkt_dev->txtime_clockid); + + seq_printf(seq, " txtime_delay: %llu\n", + (unsigned long long)pkt_dev->txtime_delay); + seq_printf(seq, " txtime_clockid: %s\n", + clockid == CLOCK_MONOTONIC ? "monotonic" : + clockid == CLOCK_REALTIME ? "realtime" : + clockid == CLOCK_TAI ? "tai" : "unknown"); + } + if (pkt_dev->xmit_mode == M_NETIF_RECEIVE) seq_puts(seq, " xmit_mode: netif_receive\n"); else if (pkt_dev->xmit_mode == M_QUEUE_XMIT) @@ -1141,6 +1157,50 @@ static ssize_t pktgen_if_write(struct file *file, (unsigned long long) pkt_dev->delay); return count; } + if (!strcmp(name, "txtime_delay")) { + max = min(10, count - i); + len = num_arg(&user_buffer[i], max, &value); + if (len < 0) + return len; + + /* in queue_xmit mode fq may clear tstamp, do not reuse skb */ + if (value > 0 && pkt_dev->clone_skb > 0) + return -EINVAL; + + WRITE_ONCE(pkt_dev->txtime_delay, (u64)value); + sprintf(pg_result, "OK: txtime_delay=%llu", + (unsigned long long)value); + return count; + } + if (!strcmp(name, "txtime_clockid")) { + char clockstr[32]; + clockid_t clk; + + memset(clockstr, 0, sizeof(clockstr)); + max = min(sizeof(clockstr) - 1, count - i); + len = strn_len(&user_buffer[i], max); + if (len < 0) + return len; + + if (copy_from_user(clockstr, &user_buffer[i], len)) + return -EFAULT; + + if (!strcmp(clockstr, "monotonic")) { + clk = CLOCK_MONOTONIC; + } else if (!strcmp(clockstr, "realtime")) { + clk = CLOCK_REALTIME; + } else if (!strcmp(clockstr, "tai")) { + clk = CLOCK_TAI; + } else { + sprintf(pg_result, "ERROR: unknown clockid '%s'", + clockstr); + return -EINVAL; + } + + sprintf(pg_result, "OK: txtime_clockid=%s", clockstr); + WRITE_ONCE(pkt_dev->txtime_clockid, clk); + return count; + } if (!strcmp(name, "rate")) { max = min(10, count - i); len = num_arg(&user_buffer[i], max, &value); @@ -1238,6 +1298,8 @@ static ssize_t pktgen_if_write(struct file *file, if (value > 0 && (pkt_dev->n_imix_entries > 0 || !(pkt_dev->flags & F_SHARED))) return -EINVAL; + if (value > 0 && READ_ONCE(pkt_dev->txtime_delay)) + return -EINVAL; pkt_dev->clone_skb = value; @@ -2321,6 +2383,21 @@ static void pktgen_setup_inject(struct pktgen_dev *pkt_dev) } +static ktime_t ktime_get_clock(clockid_t clockid) +{ + switch (clockid) { + case CLOCK_REALTIME: + return ktime_get_real(); + case CLOCK_MONOTONIC: + return ktime_get(); + case CLOCK_TAI: + return ktime_get_clocktai(); + default: + WARN_ON_ONCE(1); + return ktime_get(); + } +} + static void spin(struct pktgen_dev *pkt_dev, ktime_t spin_until) { ktime_t start_time, end_time; @@ -3510,7 +3587,8 @@ static void pktgen_wait_for_skb(struct pktgen_dev *pkt_dev) static void pktgen_xmit(struct pktgen_dev *pkt_dev) { - bool skb_shared = !!(READ_ONCE(pkt_dev->flags) & F_SHARED); + u32 flags = READ_ONCE(pkt_dev->flags); + bool skb_shared = !!(flags & F_SHARED); struct net_device *odev = pkt_dev->odev; struct netdev_queue *txq; unsigned int burst = 1; @@ -3545,6 +3623,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev) /* If no skb or clone count exhausted then get new one */ if (!pkt_dev->skb || (pkt_dev->last_ok && ++pkt_dev->clone_count >= clone_skb)) { + u64 txtime_delay; + /* build a new pkt */ kfree_skb(pkt_dev->skb); @@ -3557,6 +3637,16 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev) } pkt_dev->last_pkt_size = pkt_dev->skb->len; pkt_dev->clone_count = 0; /* reset counter */ + + txtime_delay = READ_ONCE(pkt_dev->txtime_delay); + if (flags & F_TXTIME && txtime_delay) { + clockid_t clk = READ_ONCE(pkt_dev->txtime_clockid); + ktime_t txtime = ktime_add_ns(ktime_get_clock(clk), + txtime_delay); + + skb_set_delivery_type_by_clockid(pkt_dev->skb, txtime, + clk); + } } if (pkt_dev->delay && pkt_dev->last_ok) @@ -3869,6 +3959,7 @@ static int pktgen_add_device(struct pktgen_thread *t, const char *ifname) pkt_dev->burst = 1; pkt_dev->node = NUMA_NO_NODE; pkt_dev->flags = F_SHARED; /* SKB shared by default */ + pkt_dev->txtime_clockid = CLOCK_MONOTONIC; err = pktgen_setup_dev(t->net, pkt_dev, ifname); if (err) -- 2.55.0.229.g6434b31f56-goog