Subject: Re: [ethtool] ethtool: fix netlink bitmasks when sent as NOMASK

From: Jamie Gloudon <[email-masked]>
Date: Mon, 27 Jul 2020 18:02:15 -0400

On Mon, Jul 27, 2020 at 02:51:28PM -0700, Jacob Keller wrote:
>
>
> On 7/27/2020 2:47 PM, Jacob Keller wrote:
> > The ethtool netlink API can send bitsets without an associated bitmask.
> > These do not get displayed properly, because the dump_link_modes, and
> > bitset_get_bit to not check whether the provided bitset is a NOMASK
> > bitset. This results in the inability to display peer advertised link
> > modes.
> >
> > The dump_link_modes and bitset_get_bit functions are designed so they
> > can print either the values or the mask. For a nomask bitmap, this
> > doesn't make sense. There is no mask.
> >
> > Modify dump_link_modes to check ETHTOOL_A_BITSET_NOMASK. For compact
> > bitmaps, always check and print the ETHTOOL_A_BITSET_VALUE bits,
> > regardless of the request to display the mask or the value. For full
> > size bitmaps, the set of provided bits indicates the valid values,
> > without using ETHTOOL_A_BITSET_VALUE fields. Thus, do not skip printing
> > bits without this attribute if nomask is set. This essentially means
> > that dump_link_modes will treat a NOMASK bitset as having a mask
> > equivalent to all of its set bits.
> >
> > For bitset_get_bit, also check for ETHTOOL_A_BITSET_NOMASK. For compact
> > bitmaps, always use ETHTOOL_A_BITSET_BIT_VALUE as in dump_link_modes.
> > For full bitmaps, if nomask is set, then always return true of the bit
> > is in the set, rather than only if it provides an
> > ETHTOOL_A_BITSET_BIT_VALUE. This will then correctly report the set
> > bits.
> >
> > This fixes display of link partner advertised fields when using the
> > netlink API.
> >
> > Reported-by: Jamie Gloudon <[email-masked]>
> > Signed-off-by: Jacob Keller <[email-masked]>
>
> Andrew, could you kindly test this in your setup? I believe it will
> fully resolve the issue.
>
> Michal, I think this is complete based on the docs in
> ethtool-netlink.rst and some tests. Any further insight?
>
> Thanks,
> Jake
>
> > ---
> >  netlink/bitset.c   | 9 ++++++---
> >  netlink/settings.c | 8 +++++---
> >  2 files changed, 11 insertions(+), 6 deletions(-)
> >
> > diff --git a/netlink/bitset.c b/netlink/bitset.c
> > index 130bcdb5b52c..ba5d3ea77ff7 100644
> > --- a/netlink/bitset.c
> > +++ b/netlink/bitset.c
> > @@ -50,6 +50,7 @@ bool bitset_get_bit(const struct nlattr *bitset, bool mask, unsigned int idx,
> >  	DECLARE_ATTR_TB_INFO(bitset_tb);
> >  	const struct nlattr *bits;
> >  	const struct nlattr *bit;
> > +	bool nomask;
> >  	int ret;
> >
> >  	*retptr = 0;
> > @@ -57,8 +58,10 @@ bool bitset_get_bit(const struct nlattr *bitset, bool mask, unsigned int idx,
> >  	if (ret < 0)
> >  		goto err;
> >
> > -	bits = mask ? bitset_tb[ETHTOOL_A_BITSET_MASK] :
> > -		      bitset_tb[ETHTOOL_A_BITSET_VALUE];
> > +	nomask = bitset_tb[ETHTOOL_A_BITSET_NOMASK];
> > +
> > +	bits = mask && !nomask ? bitset_tb[ETHTOOL_A_BITSET_MASK] :
> > +		                 bitset_tb[ETHTOOL_A_BITSET_VALUE];
> >  	if (bits) {
> >  		const uint32_t *bitmap =
> >  			(const uint32_t *)mnl_attr_get_payload(bits);
> > @@ -87,7 +90,7 @@ bool bitset_get_bit(const struct nlattr *bitset, bool mask, unsigned int idx,
> >
> >  		my_idx = mnl_attr_get_u32(tb[ETHTOOL_A_BITSET_BIT_INDEX]);
> >  		if (my_idx == idx)
> > -			return mask || tb[ETHTOOL_A_BITSET_BIT_VALUE];
> > +			return mask || nomask || tb[ETHTOOL_A_BITSET_BIT_VALUE];
> >  	}
> >
> >  	return false;
> > diff --git a/netlink/settings.c b/netlink/settings.c
> > index 35ba2f5dd6d5..29557653336e 100644
> > --- a/netlink/settings.c
> > +++ b/netlink/settings.c
> > @@ -280,9 +280,11 @@ int dump_link_modes(struct nl_context *nlctx, const struct nlattr *bitset,
> >  	const struct nlattr *bit;
> >  	bool first = true;
> >  	int prev = -2;
> > +	bool nomask;
> >  	int ret;
> >
> >  	ret = mnl_attr_parse_nested(bitset, attr_cb, &bitset_tb_info);
> > +	nomask = bitset_tb[ETHTOOL_A_BITSET_NOMASK];
> >  	bits = bitset_tb[ETHTOOL_A_BITSET_BITS];
> >  	if (ret < 0)
> >  		goto err_nonl;
> > @@ -297,8 +299,8 @@ int dump_link_modes(struct nl_context *nlctx, const struct nlattr *bitset,
> >  			goto err_nonl;
> >  		lm_strings = global_stringset(ETH_SS_LINK_MODES,
> >  					      nlctx->ethnl2_socket);
> > -		bits = mask ? bitset_tb[ETHTOOL_A_BITSET_MASK] :
> > -			      bitset_tb[ETHTOOL_A_BITSET_VALUE];
> > +		bits = mask && !nomask ? bitset_tb[ETHTOOL_A_BITSET_MASK] :
> > +			                 bitset_tb[ETHTOOL_A_BITSET_VALUE];
> >  		ret = -EFAULT;
> >  		if (!bits || !bitset_tb[ETHTOOL_A_BITSET_SIZE])
> >  			goto err_nonl;
> > @@ -354,7 +356,7 @@ int dump_link_modes(struct nl_context *nlctx, const struct nlattr *bitset,
> >  		if (!tb[ETHTOOL_A_BITSET_BIT_INDEX] ||
> >  		    !tb[ETHTOOL_A_BITSET_BIT_NAME])
> >  			goto err;
> > -		if (!mask && !tb[ETHTOOL_A_BITSET_BIT_VALUE])
> > +		if (!mask && !nomask && !tb[ETHTOOL_A_BITSET_BIT_VALUE])
> >  			continue;
> >
> >  		idx = mnl_attr_get_u32(tb[ETHTOOL_A_BITSET_BIT_INDEX]);
> >

I can confirm that your patch works. As you can see below:

	Link partner advertised pause frame use: Symmetric Receive-only
        Link partner advertised auto-negotiation: Yes
	Link partner advertised FEC modes: No

You can tag this patch Tested-by me. Thanks!

Regards,
Jamie Gloudon