Re: [PATCH RFC net-next 1/6] sock: MSG_PEEK support for sk_error_queue
From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: 2018-01-17 23:51:37
On Wed, Jan 17, 2018 at 7:19 AM, Sowmini Varadhan [off-list ref] wrote:
Allow the application the ability to use MSG_PEEK with sk_error_queue so that it can peek and re-read message in cases where MSG_TRUNC may be encountered. Signed-off-by: Sowmini Varadhan <redacted>
quoted hunk ↗ jump to hunk
int sock_recv_errqueue(struct sock *sk, struct msghdr *msg, int len, - int level, int type) + int level, int type, int flags) { struct sock_exterr_skb *serr; struct sk_buff *skb;@@ -2916,7 +2916,10 @@ int sock_recv_errqueue(struct sock *sk, struct msghdr *msg, int len, err = copied; out_free_skb: - kfree_skb(skb); + if (likely(!(flags & MSG_PEEK))) + kfree_skb(skb); + else + skb_queue_head(&sk->sk_error_queue, skb);
This can cause reordering with parallel readers. Can we avoid the need for peeking? It also caused a slew of subtle bugs previously. How about just define a max number of cookies and require the caller to always read with sufficient room to hold them?