Re: [PATCH net-next v2 1/6] gtp: make GTP sockets in gtp_newlink optional

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Jan 30, 2017 at 05:37:08PM +0100, Andreas Schultz wrote:
> Having both GTPv0-U and GTPv1-U is not always desirable.
> Fallback from GTPv1-U to GTPv0-U was depreciated from 3GPP
> Rel-8 onwards. Post Rel-8 implementation are discuraged
> from listening on the v0 port (see 3GPP TS 29.281, Sect. 1).
> 
> A future change will completely decouple the sockets from the
> network device. Till then, at least one of the sockets needs to
> be specified (either v0 or v1), the other is optional.
> 
> Signed-off-by: Andreas Schultz <aschultz@tpip.net>
> ---
>  drivers/net/gtp.c | 142 +++++++++++++++++++++++++++++-------------------------
>  1 file changed, 76 insertions(+), 66 deletions(-)
> 
> diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
> index bda0c64..18944f4 100644
> --- a/drivers/net/gtp.c
> +++ b/drivers/net/gtp.c
> @@ -259,28 +259,30 @@ static int gtp1u_udp_encap_recv(struct gtp_dev *gtp, struct sk_buff *skb,
>  	return iptunnel_pull_header(skb, hdrlen, skb->protocol, xnet);
>  }
>  
> -static void gtp_encap_disable(struct gtp_dev *gtp)
> -{
> -	if (gtp->sock0 && gtp->sock0->sk) {
> -		udp_sk(gtp->sock0->sk)->encap_type = 0;
> -		rcu_assign_sk_user_data(gtp->sock0->sk, NULL);
> -	}
> -	if (gtp->sock1u && gtp->sock1u->sk) {
> -		udp_sk(gtp->sock1u->sk)->encap_type = 0;
> -		rcu_assign_sk_user_data(gtp->sock1u->sk, NULL);
> -	}
> -
> -	gtp->sock0 = NULL;
> -	gtp->sock1u = NULL;
> -}
> -
>  static void gtp_encap_destroy(struct sock *sk)
>  {
>  	struct gtp_dev *gtp;
>  
>  	gtp = rcu_dereference_sk_user_data(sk);
> -	if (gtp)
> -		gtp_encap_disable(gtp);
> +	if (gtp) {
> +		udp_sk(sk)->encap_type = 0;
> +		rcu_assign_sk_user_data(sk, NULL);
> +	}
> +}
> +
> +static void gtp_encap_disable_sock(struct socket *sock)

Nitpick: Please, use sk for consistency:

        static void gtp_encap_disable_sock(struct socket *sk)

> +{
> +	if (!sock || !sock->sk)
> +		return;
> +
> +	gtp_encap_destroy(sock->sk);
> +	sockfd_put(sock);

This socket is created by userspace. If we hold it and the userspace
daemon stops without cleaning up configuration, we keep this socket
around that we cannot remove.

That's why we didn't hold any reference to this so far. I guess you
need this because of your follow up patch that catches this in the gtp
instance structure, that's why this slipped through.

> +}
> +
> +static void gtp_encap_disable(struct gtp_dev *gtp)
> +{
> +	gtp_encap_disable_sock(gtp->sock0);
> +	gtp_encap_disable_sock(gtp->sock1u);
>  }
>  
>  /* UDP encapsulation receive handler. See net/ipv4/udp.c.
> @@ -640,27 +642,24 @@ static void gtp_link_setup(struct net_device *dev)
>  
>  static int gtp_hashtable_new(struct gtp_dev *gtp, int hsize);
>  static void gtp_hashtable_free(struct gtp_dev *gtp);
> -static int gtp_encap_enable(struct net_device *dev, struct gtp_dev *gtp,
> -			    int fd_gtp0, int fd_gtp1);
> +static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[]);
> +static void gtp_encap_disable(struct gtp_dev *gtp);
>  
>  static int gtp_newlink(struct net *src_net, struct net_device *dev,
>  			struct nlattr *tb[], struct nlattr *data[])
>  {
> -	int hashsize, err, fd0, fd1;
> +	int hashsize, err;
>  	struct gtp_dev *gtp;
>  	struct gtp_net *gn;

Nitpick: We prefer declarations in this order:

  	struct gtp_dev *gtp;
  	struct gtp_net *gn;
	int hashsize, err;

>From longest line to shorter. I know we break this rule in many spots,
but it would be good if you keep this in mind.

> -	if (!data[IFLA_GTP_FD0] || !data[IFLA_GTP_FD1])
> +	if (!data[IFLA_GTP_FD0] && !data[IFLA_GTP_FD1])
>  		return -EINVAL;
>  
>  	gtp = netdev_priv(dev);
>  
> -	fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
> -	fd1 = nla_get_u32(data[IFLA_GTP_FD1]);
> -
> -	err = gtp_encap_enable(dev, gtp, fd0, fd1);
> +	err = gtp_encap_enable(gtp, data);
>  	if (err < 0)
> -		goto out_err;
> +		return err;
>  
>  	if (!data[IFLA_GTP_PDP_HASHSIZE])
>  		hashsize = 1024;
> @@ -688,7 +687,6 @@ static int gtp_newlink(struct net *src_net, struct net_device *dev,
>  	gtp_hashtable_free(gtp);
>  out_encap:
>  	gtp_encap_disable(gtp);
> -out_err:
>  	return err;
>  }
>  
> @@ -803,61 +801,73 @@ static void gtp_hashtable_free(struct gtp_dev *gtp)
>  	kfree(gtp->tid_hash);
>  }
>  
> -static int gtp_encap_enable(struct net_device *dev, struct gtp_dev *gtp,
> -			    int fd_gtp0, int fd_gtp1)
> +static struct socket *gtp_encap_enable_socket(int fd, int type,
> +					      struct gtp_dev *gtp)
>  {
>  	struct udp_tunnel_sock_cfg tuncfg = {NULL};
> -	struct socket *sock0, *sock1u;
> +	struct socket *sock;
>  	int err;
>  
> -	netdev_dbg(dev, "enable gtp on %d, %d\n", fd_gtp0, fd_gtp1);
> +	pr_debug("enable gtp on %d, %d\n", fd, type);
>  
> -	sock0 = sockfd_lookup(fd_gtp0, &err);
> -	if (sock0 == NULL) {
> -		netdev_dbg(dev, "socket fd=%d not found (gtp0)\n", fd_gtp0);
> -		return -ENOENT;
> +	sock = sockfd_lookup(fd, &err);
> +	if (!sock) {
> +		pr_debug("gtp socket fd=%d not found\n", fd);
> +		return NULL;
>  	}
>  
> -	if (sock0->sk->sk_protocol != IPPROTO_UDP) {
> -		netdev_dbg(dev, "socket fd=%d not UDP\n", fd_gtp0);
> +	if (sock->sk->sk_protocol != IPPROTO_UDP) {
> +		pr_debug("socket fd=%d not UDP\n", fd);

I would suggest you submit an initial patch to cover all this
conversion from netdev_dbg() to pr_debug() in first place, so we don't
do this here.

>  		err = -EINVAL;
> -		goto err1;
> +		goto out_sock;
>  	}
>  
> -	sock1u = sockfd_lookup(fd_gtp1, &err);
> -	if (sock1u == NULL) {
> -		netdev_dbg(dev, "socket fd=%d not found (gtp1u)\n", fd_gtp1);
> -		err = -ENOENT;
> -		goto err1;
> +	if (rcu_dereference_sk_user_data(sock->sk)) {
> +		err = -EBUSY;
> +		goto out_sock;
>  	}
>  
> -	if (sock1u->sk->sk_protocol != IPPROTO_UDP) {
> -		netdev_dbg(dev, "socket fd=%d not UDP\n", fd_gtp1);
> -		err = -EINVAL;
> -		goto err2;
> -	}
> -
> -	netdev_dbg(dev, "enable gtp on %p, %p\n", sock0, sock1u);
> -
> -	gtp->sock0 = sock0;
> -	gtp->sock1u = sock1u;
> -
>  	tuncfg.sk_user_data = gtp;
> +	tuncfg.encap_type = type;
>  	tuncfg.encap_rcv = gtp_encap_recv;
>  	tuncfg.encap_destroy = gtp_encap_destroy;
>  
> -	tuncfg.encap_type = UDP_ENCAP_GTP0;
> -	setup_udp_tunnel_sock(sock_net(gtp->sock0->sk), gtp->sock0, &tuncfg);
> -
> -	tuncfg.encap_type = UDP_ENCAP_GTP1U;
> -	setup_udp_tunnel_sock(sock_net(gtp->sock1u->sk), gtp->sock1u, &tuncfg);
> -
> -	err = 0;
> -err2:
> -	sockfd_put(sock1u);
> -err1:
> -	sockfd_put(sock0);
> -	return err;
> +	setup_udp_tunnel_sock(sock_net(sock->sk), sock, &tuncfg);
> +	return sock;
> +
> +out_sock:
> +	sockfd_put(sock);
> +	return ERR_PTR(err);
> +}
> +
> +static int gtp_encap_enable(struct gtp_dev *gtp, struct nlattr *data[])
> +{
> +	struct socket *sock0 = NULL;
> +	struct socket *sock1u = NULL;

Same thing here regarding socket declaration.

> +	if (data[IFLA_GTP_FD0]) {
> +		u32 fd0 = nla_get_u32(data[IFLA_GTP_FD0]);
> +
> +		sock0 = gtp_encap_enable_socket(fd0, UDP_ENCAP_GTP0, gtp);
> +		if (IS_ERR(sock0))
> +			return PTR_ERR(sock0);
> +	}
> +
> +	if (data[IFLA_GTP_FD1]) {
> +		u32 fd1 = nla_get_u32(data[IFLA_GTP_FD1]);
> +
> +		sock1u = gtp_encap_enable_socket(fd1, UDP_ENCAP_GTP1U, gtp);
> +		if (IS_ERR(sock1u)) {
> +			if (sock0)
> +				sockfd_put(sock0);
> +			return PTR_ERR(sock1u);
> +		}
> +	}
> +
> +	gtp->sock0 = sock0;
> +	gtp->sock1u = sock1u;
> +
> +	return 0;
>  }
>  
>  static struct net_device *gtp_find_dev(struct net *net, int ifindex)
> -- 
> 2.10.2
>