netdev - Re: ethtool 5.7: --change commands fail

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Message-ID: <20200725125433.igpkdwd26dxesxno@lion.mk-sys.cz>
Date:   Sat, 25 Jul 2020 14:54:33 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Ali MJ Al-Nasrawy <alimjalnasrawy@...il.com>
Cc:     netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>
Subject: Re: ethtool 5.7: --change commands fail

On Sat, Jul 25, 2020 at 09:49:36AM +0300, Ali MJ Al-Nasrawy wrote:
> ethtool: v5.7
> kernel: v5.4.52
> driver: r8169 + libphy
> 
> Starting from v5.7, all ethtool --change commands fail to apply and
> show the following error message:
> 
> $ ethtool -s ens5 autoneg off
> netlink error: No such file or directory
> Cannot set new settings: No such file or directory
>   not setting autoneg
> 
> 'git bisect' points to:
> 8bb9a04 (ethtool.c: Report transceiver correctly)
> 
> After debugging I found that this commit sets deprecated.transceiver
> and then do_ioctl_slinksettings() checks for it and returns -1.
> errno is thus invalid and the the error message is bogus.
> 
> With debugging enabled:
> 
> $ ethtool --debug 0xffff -s ens5 autoneg off
> sending genetlink packet (32 bytes):
>     msg length 32 genl-ctrl
>     CTRL_CMD_GETFAMILY
>         CTRL_ATTR_FAMILY_NAME = "ethtool"
> <message dump/>
> received genetlink packet (52 bytes):
>     msg length 52 error errno=-2
> <message dump/>
> netlink error: No such file or directory
> offending message:
>     ETHTOOL_MSG_LINKINFO_SET
>         ETHTOOL_A_LINKINFO_PORT = 101
> Cannot set new settings: No such file or directory
>   not setting autoneg

Kernel 5.4.x does not support ethtool netlink so that we fall back to
ioctl. While we want to report transceiver in "ethtool <dev>" output, we
must not pass the value retrieved from kernel back to kernel when
"ethtool -s <dev> ..." command is executed.

Does the patch below help in your setup?

Michal


diff --git a/ethtool.c b/ethtool.c
index d37c223dcc04..1b99ac91dcbf 100644
--- a/ethtool.c
+++ b/ethtool.c
@@ -2906,6 +2906,8 @@ static int do_sset(struct cmd_context *ctx)
 		struct ethtool_link_usettings *link_usettings;
 
 		link_usettings = do_ioctl_glinksettings(ctx);
+		memset(&link_usettings->deprecated, 0,
+		       sizeof(link_usettings->deprecated));
 		if (link_usettings == NULL)
 			link_usettings = do_ioctl_gset(ctx);
 		if (link_usettings == NULL) {