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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Willem de Bruijn , Kuniyuki Iwashima , bpf@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH v2 bpf-next/net 1/5] ethtool: Introduce ETHTOOL_MSG_TSINFO_SET for virtual interfaces. Message-ID: References: <20260613010039.1362312-1-kuniyu@google.com> <20260613010039.1362312-2-kuniyu@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260613010039.1362312-2-kuniyu@google.com> On 06/13, Kuniyuki Iwashima wrote: > Before enabling SO_TIMESTAMPING, applications typically try to > enable hardware timestamping on network interfaces via SIOCSHWTSTAMP > (or ETHTOOL_MSG_TSCONFIG_SET). > > The timestamping capability on an interface can be checked via > ETHTOOL_MSG_TSINFO_GET: > > # ethtool -T eth0 > Time stamping parameters for eth0: > Capabilities: > hardware-transmit > software-transmit > hardware-receive > software-receive > software-system-clock > hardware-raw-clock > PTP Hardware Clock: none > Hardware Transmit Timestamp Modes: > off > on > Hardware Receive Filter Modes: > none > all > > These operations rely on the driver implementing two callbacks, > dev->netdev_ops->ndo_hwtstamp_{get,set}(). > > However, among all virtual network interfaces, only bond and > macvlan currently implement them. > > As a result, most virtual interfaces cannot advertise the > capabilities of their underlying devices: > > # ip link add ipvl0 link eth0 type ipvlan mode l2 bridge > # ethtool -T ipvl0 > Time stamping parameters for ipvl0: > Capabilities: > software-receive > software-system-clock > PTP Hardware Clock: none > Hardware Transmit Timestamp Modes: none > Hardware Receive Filter Modes: none > > While these callbacks could be implemented in each virtual > interface, this approach is limited to those directly linked > to a physical device. > > Not all virtual interfaces are tied to real hardware; for > instance, packets from UDP tunnel devices eventually pass > through physical devices and can be hardware-timestamped there. > > Let's allow configuring the hardware timestamping capability on > virtual interfaces via ETHTOOL_MSG_TSINFO_SET. I don't have a lot of state on this, but when adding xdp hw timestamping I remember fighting a lot with those apis. Now we are adding another one, but (seemingly?) for sw devices. Can you explain a bit more about why can't existing SIOCGHWTSTAMP (or ETHTOOL_MSG_TSCONFIG_SET) fallback to your new dev->tsinfo.enabled codepaths for the devices that don't implement the ops?