Subject: Re: [PATCH net-next 2/3] sctp: add sock_reuseport for the sock in __sctp_hash_endpoint

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Mon, 22 Oct 2018 11:15:47 -0300

On Sun, Oct 21, 2018 at 12:43:37PM +0800, Xin Long wrote:
> This is a part of sk_reuseport support for sctp. It defines a helper
> sctp_bind_addrs_check() to check if the bind_addrs in two socks are
> matched. It will add sock_reuseport if they are completely matched,
> and return err if they are partly matched, and alloc sock_reuseport
> if all socks are not matched at all.
> 
> It will work until sk_reuseport support is added in
> sctp_get_port_local() in the next patch.
> 
> Signed-off-by: Xin Long <[email-masked]>
> ---
>  include/net/sctp/sctp.h    |  2 +-
>  include/net/sctp/structs.h |  2 ++
>  net/core/sock_reuseport.c  |  1 +
>  net/sctp/bind_addr.c       | 28 ++++++++++++++++++++++
>  net/sctp/input.c           | 60 +++++++++++++++++++++++++++++++++++++++-------
>  net/sctp/socket.c          |  3 +--
>  6 files changed, 85 insertions(+), 11 deletions(-)
> 
> diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
> index 8c2caa3..b8cd58d 100644
> --- a/include/net/sctp/sctp.h
> +++ b/include/net/sctp/sctp.h
> @@ -152,7 +152,7 @@ int sctp_primitive_RECONF(struct net *net, struct sctp_association *asoc,
>   */
>  int sctp_rcv(struct sk_buff *skb);
>  void sctp_v4_err(struct sk_buff *skb, u32 info);
> -void sctp_hash_endpoint(struct sctp_endpoint *);
> +int sctp_hash_endpoint(struct sctp_endpoint *ep);
>  void sctp_unhash_endpoint(struct sctp_endpoint *);
>  struct sock *sctp_err_lookup(struct net *net, int family, struct sk_buff *,
>  			     struct sctphdr *, struct sctp_association **,
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index a11f937..15d017f 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -1190,6 +1190,8 @@ int sctp_bind_addr_conflict(struct sctp_bind_addr *, const union sctp_addr *,
>  			 struct sctp_sock *, struct sctp_sock *);
>  int sctp_bind_addr_state(const struct sctp_bind_addr *bp,
>  			 const union sctp_addr *addr);
> +int sctp_bind_addrs_check(struct sctp_sock *sp,
> +			  struct sctp_sock *sp2, int cnt2);
>  union sctp_addr *sctp_find_unmatch_addr(struct sctp_bind_addr	*bp,
>  					const union sctp_addr	*addrs,
>  					int			addrcnt,
> diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
> index ba5cba5..d8fe3e5 100644
> --- a/net/core/sock_reuseport.c
> +++ b/net/core/sock_reuseport.c
> @@ -187,6 +187,7 @@ int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
>  		call_rcu(&old_reuse->rcu, reuseport_free_rcu);
>  	return 0;
>  }
> +EXPORT_SYMBOL(reuseport_add_sock);
>  
>  void reuseport_detach_sock(struct sock *sk)
>  {
> diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
> index 7df3704..78d0d93 100644
> --- a/net/sctp/bind_addr.c
> +++ b/net/sctp/bind_addr.c
> @@ -337,6 +337,34 @@ int sctp_bind_addr_match(struct sctp_bind_addr *bp,
>  	return match;
>  }
>  
> +int sctp_bind_addrs_check(struct sctp_sock *sp,
> +			  struct sctp_sock *sp2, int cnt2)
> +{
> +	struct sctp_bind_addr *bp2 = &sp2->ep->base.bind_addr;
> +	struct sctp_bind_addr *bp = &sp->ep->base.bind_addr;
> +	struct sctp_sockaddr_entry *laddr, *laddr2;
> +	bool exist = false;
> +	int cnt = 0;
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(laddr, &bp->address_list, list) {
> +		list_for_each_entry_rcu(laddr2, &bp2->address_list, list) {
> +			if (sp->pf->af->cmp_addr(&laddr->a, &laddr2->a) &&
> +			    laddr->valid == laddr2->valid) {

I think by here in the normal run laddr2->valid will always be true,
but as is it gives the impression that it accepts 0 == 0 too, which
would be bad.  May be on a fast BINDX_REM/BINDX_ADD it could trigger
laddr2->valid = 0 in there, not sure.

Anyway, may be '... laddr->valid && laddr2->valid' instead or you
really want to allow the 0 == 0 case?

> +				exist = true;
> +				goto next;
> +			}
> +		}
> +		cnt = 0;
> +		break;
> +next:
> +		cnt++;
> +	}
> +	rcu_read_unlock();
> +
> +	return (cnt == cnt2) ? 0 : (exist ? -EEXIST : 1);
> +}
> +
>  /* Does the address 'addr' conflict with any addresses in
>   * the bp.
>   */
> diff --git a/net/sctp/input.c b/net/sctp/input.c
> index 60ede89..6bfeb10 100644
> --- a/net/sctp/input.c
> +++ b/net/sctp/input.c
> @@ -723,43 +723,87 @@ static int sctp_rcv_ootb(struct sk_buff *skb)
>  }
>  
>  /* Insert endpoint into the hash table.  */
> -static void __sctp_hash_endpoint(struct sctp_endpoint *ep)
> +static int __sctp_hash_endpoint(struct sctp_endpoint *ep)
>  {
> -	struct net *net = sock_net(ep->base.sk);
> -	struct sctp_ep_common *epb;
> +	struct sock *sk = ep->base.sk;
> +	struct net *net = sock_net(sk);
>  	struct sctp_hashbucket *head;
> +	struct sctp_ep_common *epb;
>  
>  	epb = &ep->base;
> -
>  	epb->hashent = sctp_ep_hashfn(net, epb->bind_addr.port);
>  	head = &sctp_ep_hashtable[epb->hashent];
>  
> +	if (sk->sk_reuseport) {
> +		bool any = sctp_is_ep_boundall(sk);
> +		struct sctp_ep_common *epb2;
> +		struct list_head *list;
> +		int cnt = 0, err = 1;
> +
> +		list_for_each(list, &ep->base.bind_addr.address_list)
> +			cnt++;
> +
> +		sctp_for_each_hentry(epb2, &head->chain) {
> +			struct sock *sk2 = epb2->sk;
> +
> +			if (!net_eq(sock_net(sk2), net) || sk2 == sk ||
> +			    !uid_eq(sock_i_uid(sk2), sock_i_uid(sk)) ||
> +			    !sk2->sk_reuseport)
> +				continue;
> +
> +			err = sctp_bind_addrs_check(sctp_sk(sk2),
> +						    sctp_sk(sk), cnt);
> +			if (!err) {
> +				err = reuseport_add_sock(sk, sk2, any);
> +				if (err)
> +					return err;
> +				break;
> +			} else if (err < 0) {
> +				return err;
> +			}
> +		}
> +
> +		if (err) {
> +			err = reuseport_alloc(sk, any);
> +			if (err)
> +				return err;
> +		}
> +	}
> +
>  	write_lock(&head->lock);
>  	hlist_add_head(&epb->node, &head->chain);
>  	write_unlock(&head->lock);
> +	return 0;
>  }
>  
>  /* Add an endpoint to the hash. Local BH-safe. */
> -void sctp_hash_endpoint(struct sctp_endpoint *ep)
> +int sctp_hash_endpoint(struct sctp_endpoint *ep)
>  {
> +	int err;
> +
>  	local_bh_disable();
> -	__sctp_hash_endpoint(ep);
> +	err = __sctp_hash_endpoint(ep);
>  	local_bh_enable();
> +
> +	return err;
>  }
>  
>  /* Remove endpoint from the hash table.  */
>  static void __sctp_unhash_endpoint(struct sctp_endpoint *ep)
>  {
> -	struct net *net = sock_net(ep->base.sk);
> +	struct sock *sk = ep->base.sk;
>  	struct sctp_hashbucket *head;
>  	struct sctp_ep_common *epb;
>  
>  	epb = &ep->base;
>  
> -	epb->hashent = sctp_ep_hashfn(net, epb->bind_addr.port);
> +	epb->hashent = sctp_ep_hashfn(sock_net(sk), epb->bind_addr.port);
>  
>  	head = &sctp_ep_hashtable[epb->hashent];
>  
> +	if (rcu_access_pointer(sk->sk_reuseport_cb))
> +		reuseport_detach_sock(sk);
> +
>  	write_lock(&head->lock);
>  	hlist_del_init(&epb->node);
>  	write_unlock(&head->lock);
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index fc0386e..44e7d8c 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -7850,8 +7850,7 @@ static int sctp_listen_start(struct sock *sk, int backlog)
>  	}
>  
>  	sk->sk_max_ack_backlog = backlog;
> -	sctp_hash_endpoint(ep);
> -	return 0;
> +	return sctp_hash_endpoint(ep);
>  }
>  
>  /*
> -- 
> 2.1.0
>