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Miller" , Jakub Kicinski , Paolo Abeni Cc: Willem de Bruijn , Simon Horman , netdev@vger.kernel.org, Eric Dumazet , stable@vger.kernel.org, Tony Nguyen , Przemek Kitszel , Andrew Lunn Subject: [PATCH net] ixgbe: reserve TX timestamp after skb preparation Date: Mon, 26 Oct 2026 09:20:35 +0100 Message-ID: <20261026082035.335770-1-edumazet@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ixgbe_xmit_frame_ring() takes an extra skb reference with skb_get() for the pending TX timestamp before preparing the skb for transmit. Several of the following steps may need to reallocate the skb head: - ixgbe_tso() calls skb_cow_head(), which reaches pskb_expand_head() when the header is cloned (e.g. a packet tap holds a clone). - ixgbe_tx_csum() falls back to skb_checksum_help() for unsupported checksum offsets, which can call pskb_expand_head() through skb_ensure_writable(). - With DCB and a software VLAN tag, skb_cow_head() is called to rewrite the VLAN priority. pskb_expand_head() used to BUG() on shared skbs. Since commit c7d8bc3dd511 ("net: skbuff: don't BUG() on bad arguments to pskb_expand_head()") it returns -EINVAL instead, so these packets are dropped (TSO, DCB) or sent with an unfinished checksum (skb_checksum_help() errors are ignored by ixgbe_tx_csum()). Reserve the TX timestamp right before ixgbe_tx_map(), after all skb preparation, as i40e and ice already do. The timestamp request remains covered on the FCoE path, and the cleanup on ixgbe_tx_map() failure is unchanged. Fixes: 891dc0821d20 ("ixgbe: Add ptp work item to poll for the Tx timestamp") Cc: stable@vger.kernel.org Signed-off-by: Eric Dumazet --- Cc: Tony Nguyen Cc: Przemek Kitszel Cc: Andrew Lunn --- drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 40 +++++++++++-------- 1 file changed, 23 insertions(+), 17 deletions(-) diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c index f91856498eb2d9e0e4173153c8c00bc2248bb708..b9496f0bee1312499f28c2f3c24fcff9a1e66e0d 100644 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c @@ -9444,23 +9444,6 @@ netdev_tx_t ixgbe_xmit_frame_ring(struct sk_buff *skb, } protocol = vlan_get_protocol(skb); - if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) && - adapter->ptp_clock) { - if (adapter->tstamp_config.tx_type == HWTSTAMP_TX_ON && - !test_and_set_bit_lock(__IXGBE_PTP_TX_IN_PROGRESS, - &adapter->state)) { - skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS; - tx_flags |= IXGBE_TX_FLAGS_TSTAMP; - - /* schedule check for Tx timestamp */ - adapter->ptp_tx_skb = skb_get(skb); - adapter->ptp_tx_start = jiffies; - schedule_work(&adapter->ptp_tx_work); - } else { - adapter->tx_hwtstamp_skipped++; - } - } - #ifdef CONFIG_PCI_IOV /* * Use the l2switch_enable flag - would be false if the DMA @@ -9525,6 +9508,29 @@ netdev_tx_t ixgbe_xmit_frame_ring(struct sk_buff *skb, #ifdef IXGBE_FCOE xmit_fcoe: #endif /* IXGBE_FCOE */ + /* Reserve the Tx timestamp only after all skb preparation: + * skb_get() makes the skb shared, and pskb_expand_head() + * (reached from skb_cow_head() or skb_checksum_help()) + * refuses shared skbs. + */ + if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) && + adapter->ptp_clock) { + if (adapter->tstamp_config.tx_type == HWTSTAMP_TX_ON && + !test_and_set_bit_lock(__IXGBE_PTP_TX_IN_PROGRESS, + &adapter->state)) { + skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS; + tx_flags |= IXGBE_TX_FLAGS_TSTAMP; + first->tx_flags |= IXGBE_TX_FLAGS_TSTAMP; + + /* schedule check for Tx timestamp */ + adapter->ptp_tx_skb = skb_get(skb); + adapter->ptp_tx_start = jiffies; + schedule_work(&adapter->ptp_tx_work); + } else { + adapter->tx_hwtstamp_skipped++; + } + } + if (ixgbe_tx_map(tx_ring, first, hdr_len)) goto cleanup_tx_timestamp; -- 2.53.0