Subject: Re: [PATCH net-next] netlink: let core handle error cases in dump operations

From: Simon Horman <[email-masked]>
Date: Thu, 7 Mar 2024 09:35:30 +0000

+ Ido Schimmel, David Ahern

On Wed, Mar 06, 2024 at 10:24:26AM +0000, Eric Dumazet wrote:
> After commit b5a899154aa9 ("netlink: handle EMSGSIZE errors
> in the core"), we can remove some code that was not 100 % correct
> anyway.
> 
> Signed-off-by: Eric Dumazet <[email-masked]>

Thanks Eric,

this looks like a nice clean-up in combination with the cited commit.

Reviewed-by: Simon Horman <[email-masked]>

> ---
>  net/core/rtnetlink.c    | 5 +----
>  net/ipv4/devinet.c      | 4 ----
>  net/ipv4/fib_frontend.c | 7 +------
>  net/ipv6/addrconf.c     | 7 +------
>  4 files changed, 3 insertions(+), 20 deletions(-)
> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 780b330f8ef9fa4881b9d51570d1a65f5171ee5d..7eac6765df098fd685937ace63dfb5add9c77731 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -2267,11 +2267,8 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
>  				       nlh->nlmsg_seq, 0, flags,
>  				       ext_filter_mask, 0, NULL, 0,
>  				       netnsid, GFP_KERNEL);
> -		if (err < 0) {
> -			if (likely(skb->len))
> -				err = skb->len;
> +		if (err < 0)
>  			break;
> -		}
>  	}
>  	cb->seq = tgt_net->dev_base_seq;
>  	nl_dump_check_consistent(cb, nlmsg_hdr(skb));
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index 4daa8124f247c256c4f8c1ff29ac621570af0755..7a437f0d41905e6acfdc35743afba3a7abfd0dd5 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1900,8 +1900,6 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
>  			goto done;
>  	}
>  done:
> -	if (err < 0 && likely(skb->len))
> -		err = skb->len;
>  	if (fillargs.netnsid >= 0)
>  		put_net(tgt_net);
>  	rcu_read_unlock();
> @@ -2312,8 +2310,6 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
>  		ctx->all_default++;
>  	}
>  done:
> -	if (err < 0 && likely(skb->len))
> -		err = skb->len;
>  	rcu_read_unlock();
>  	return err;
>  }
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index bf3a2214fe29b6f9b494581b293259e6c5ce6f8c..48741352a88a72e0232977cc9f2cf172f45df89b 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -1026,8 +1026,6 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
>  			goto unlock;
>  		}
>  		err = fib_table_dump(tb, skb, cb, &filter);
> -		if (err < 0 && skb->len)
> -			err = skb->len;
>  		goto unlock;
>  	}
>  
> @@ -1045,11 +1043,8 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
>  				memset(&cb->args[2], 0, sizeof(cb->args) -
>  						 2 * sizeof(cb->args[0]));
>  			err = fib_table_dump(tb, skb, cb, &filter);
> -			if (err < 0) {
> -				if (likely(skb->len))
> -					err = skb->len;
> +			if (err < 0)
>  				goto out;
> -			}
>  			dumped = 1;
>  next:
>  			e++;
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 2f84e6ecf19f48602cadb47bc378c9b5a1cdbf65..f786b65d12e43c53ed36535880f6e6d35879a44e 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -793,8 +793,6 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
>  		ctx->all_default++;
>  	}
>  done:
> -	if (err < 0 && likely(skb->len))
> -		err = skb->len;
>  	rcu_read_unlock();
>  	return err;
>  }
> @@ -6158,11 +6156,8 @@ static int inet6_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
>  					NETLINK_CB(cb->skb).portid,
>  					cb->nlh->nlmsg_seq,
>  					RTM_NEWLINK, NLM_F_MULTI);
> -		if (err < 0) {
> -			if (likely(skb->len))
> -				err = skb->len;
> +		if (err < 0)
>  			break;
> -		}
>  	}
>  	rcu_read_unlock();
>  
> -- 
> 2.44.0.278.ge034bb2e1d-goog
> 
>