Subject: Re: [PATCH net-next v10 07/13] net: ethtool: Introduce a command to list PHYs on an interface

From: Jakub Kicinski <[email-masked]>
Date: Fri, 8 Mar 2024 21:18:42 -0800

On Mon,  4 Mar 2024 16:10:03 +0100 Maxime Chevallier wrote:
> +PHY_GET
> +=======
> +
> +Retrieve information about a given Ethernet PHY sitting on the link. As there
> +can be more than one PHY, the DUMP operation can be used to list the PHYs
> +present on a given interface, by passing an interface index or name in
> +the dump request

Could be worth re-stating the default behavior of the DO request?
That the DO will return the dev->phydev by default and if PHY_INDEX
is specified in the header, the particular PHY with that index?

> +	if (phydev->drv && nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, phydev->drv->name))

could you break the lines at 80 where it doesn't hurt readability?
This way:

	if (phydev->drv && 
	    nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, phydev->drv->name))

> +		return -EMSGSIZE;
> +
> +	if (ptype == PHY_UPSTREAM_PHY) {
> +		struct phy_device *upstream = pdn->upstream.phydev;
> +		const char *sfp_upstream_name;
> +
> +		/* Parent index */
> +		if (nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_INDEX, upstream->phyindex))
> +			return -EMSGSIZE;
> +
> +		if (pdn->parent_sfp_bus) {
> +			sfp_upstream_name = sfp_get_name(pdn->parent_sfp_bus);
> +			if (sfp_upstream_name && nla_put_string(skb,
> +								ETHTOOL_A_PHY_UPSTREAM_SFP_NAME,
> +								sfp_upstream_name))

ditto

> +				return -EMSGSIZE;
> +		}
> +	}

> +int ethnl_phy_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> +	struct phy_req_info req_info = {};
> +	struct nlattr **tb = info->attrs;
> +	struct sk_buff *rskb;
> +	void *reply_payload;
> +	int reply_len;
> +	int ret;
> +
> +	ret = ethnl_parse_header_dev_get(&req_info.base,
> +					 tb[ETHTOOL_A_PHY_HEADER],
> +					 genl_info_net(info), info->extack,
> +					 true);
> +	if (ret < 0)
> +		return ret;
> +
> +	rtnl_lock();
> +
> +	ret = ethnl_phy_parse_request(&req_info.base, tb);
> +	if (ret < 0)
> +		goto err_unlock_rtnl;
> +
> +	/* No PHY, return early */
> +	if (!req_info.pdn.phy)
> +		goto err_unlock_rtnl;
> +
> +	ret = ethnl_phy_reply_size(&req_info.base, info->extack);
> +	if (ret < 0)
> +		goto err_unlock_rtnl;
> +	reply_len = ret + ethnl_reply_header_size();
> +
> +	rskb = ethnl_reply_init(reply_len, req_info.base.dev,
> +				ETHTOOL_MSG_PHY_GET_REPLY,
> +				ETHTOOL_A_PHY_HEADER,
> +				info, &reply_payload);
> +	if (!rskb) {
> +		ret = -ENOMEM;
> +		goto err_unlock_rtnl;
> +	}
> +
> +	ret = ethnl_phy_fill_reply(&req_info.base, rskb);
> +	if (ret)
> +		goto err_free_msg;
> +
> +	rtnl_unlock();
> +	ethnl_parse_header_dev_put(&req_info.base);
> +	genlmsg_end(rskb, reply_payload);
> +
> +	return genlmsg_reply(rskb, info);
> +
> +err_free_msg:
> +	nlmsg_free(rskb);
> +err_unlock_rtnl:
> +	rtnl_unlock();
> +	ethnl_parse_header_dev_put(&req_info.base);
> +	return ret;
> +}
> +
> +struct ethnl_phy_dump_ctx {
> +	struct phy_req_info	*phy_req_info;
> +	unsigned long ifindex;
> +	unsigned long phy_index;
> +};
> +
> +int ethnl_phy_start(struct netlink_callback *cb)
> +{
> +	const struct genl_dumpit_info *info = genl_dumpit_info(cb);

You can save some chars by using genl_info_dump() here

> +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> +	struct nlattr **tb = info->info.attrs;

then you can ditch this

> +	int ret;
> +
> +	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
> +
> +	ctx->phy_req_info = kzalloc(sizeof(*ctx->phy_req_info), GFP_KERNEL);
> +	if (!ctx->phy_req_info)
> +		return -ENOMEM;
> +
> +	ret = ethnl_parse_header_dev_get(&ctx->phy_req_info->base,
> +					 tb[ETHTOOL_A_PHY_HEADER],

and:

					 info->attrs[ETHTOOL_A_PHY_HEADER],

> +					 sock_net(cb->skb->sk), cb->extack,
> +					 false);

leaking ctx->phy_req_info on error?

> +	ctx->ifindex = 0;
> +	ctx->phy_index = 0;
> +	return ret;
> +}

> +static int ethnl_phy_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
> +				  struct netlink_callback *cb)
> +{
> +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> +	struct phy_req_info *pri = ctx->phy_req_info;
> +	struct phy_device_node *pdn;
> +	int ret = 0;
> +	void *ehdr;
> +
> +	pri->base.dev = dev;
> +
> +	xa_for_each_start(&dev->link_topo->phys, ctx->phy_index, pdn, ctx->phy_index) {
> +		ehdr = ethnl_dump_put(skb, cb,
> +				      ETHTOOL_MSG_PHY_GET_REPLY);

this one OTOH fits on a line :)

> +		if (!ehdr) {
> +			ret = -EMSGSIZE;
> +			break;
> +		}
> +
> +		ret = ethnl_fill_reply_header(skb, dev,
> +					      ETHTOOL_A_PHY_HEADER);

ditto

> +		if (ret < 0) {
> +			genlmsg_cancel(skb, ehdr);
> +			break;
> +		}
> +
> +		memcpy(&pri->pdn, pdn, sizeof(*pdn));
> +		ret = ethnl_phy_fill_reply(&pri->base, skb);

On a DO fill() shouldn't fail, because we size the skb, but if we pack
many entries into the skb on a DUMP it can. So:

		if (ret < 0) {
			genlmsg_cancel(skb, ehdr);
			break;
		}

no?

> +		genlmsg_end(skb, ehdr);
> +	}
> +
> +	return ret;
> +}
> +
> +int ethnl_phy_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
> +{
> +	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
> +	struct net *net = sock_net(skb->sk);
> +	struct net_device *dev;
> +	int ret = 0;
> +
> +	rtnl_lock();
> +
> +	if (ctx->phy_req_info->base.dev) {
> +		ret = ethnl_phy_dump_one_dev(skb, ctx->phy_req_info->base.dev, cb);
> +	} else {
> +		for_each_netdev_dump(net, dev, ctx->ifindex) {
> +			ret = ethnl_phy_dump_one_dev(skb, dev, cb);
> +			if (ret)
> +				break;
> +
> +			ctx->phy_index = 0;
> +		}
> +	}
> +	rtnl_unlock();
> +
> +	if (ret == -EMSGSIZE && skb->len)
> +		return skb->len;

you can remove this if thanks to (very recent) commit b5a899154aa9

> +	return ret;
> +}

Very sorry for the late review, BTW :(