On 10.02.2021 01:32, Stephen Hemminger wrote: > On Tue, 9 Feb 2021 18:35:54 +0100 > Anton Hvornum <an...@hvornum.se> wrote: > >> Hi. >> >> I am a bit new to ethtool, kernel drivers and all the surrounding aspects. >> I also recognize that my use case is of low priority and a bit niche, >> but any response would be greatly appreciated. >> >> I'm modifying an existing Intel driver, and I'm looking for a way to >> integrate/add another ethtool hook to force call `netif_carrier_on`. >> There's plenty of hooks/listeners (not clear as to what you call >> these) between the Intel driver and ethtool via C API's today that >> allows for ethtool to control the driver. Many of which are for speed, >> autonegotiation etc. But I don't see any flags/functions to force a >> carrier state to up. >> >> This would be very useful for many reasons, primarily on fiber optic >> setups where you are developing hardware such as switches, routers and >> even developing network cards. Or if you've got a passive device such >> as IDS or something similar that passively monitors network traffic >> and can't/shouldn't send out link requests. >> There are commercial products with modified drivers that support this, >> but since the Intel hardware in this case seems to support it - just >> that there's no way controlling it with the tools that exist today. I >> would therefore request a feature for consideration to ethtool that >> can force carrier states up/down. >> >> A intuitive option I think would be: >> ethtool --change carrier on >> >> Assuming that drivers follow suit and allow this. But a first step >> would be for the tools to support it in the API so drivers have >> something to call/listen for. In the meantime, I can probably >> integrate a private flag and go that route, but that feels hacky and >> won't foster driver developers to follow suit. My goal is to empower >> more open source alternatives to otherwise expensive commercials >> solutions. >> >> Best wishes, >> Anton Hvornum > > Normally, carrier just reflects the state of what the hardware is > reporting. Why not set admin down which tells the NIC to take > the device offline, and that drops the fiber link. > > Or maybe what you want is already there. > Try writing to /sys/class/net/ethX/carrier which forces a carrier change? >
This attribute uses callback ndo_change_carrier in struct net_device_ops. The kerneldoc provides further details.
