Subject: Re: [PATCH v2 11/12] l2tp: Add support for static unmanaged L2TPv3 tunnels

From: James Chapman <[email-masked]>
Date: Mon, 29 Mar 2010 11:52:34 +0100

Eric Dumazet wrote:
> Le lundi 29 mars 2010 à 10:57 +0100, James Chapman a écrit :
>> This patch adds support for static (unmanaged) L2TPv3 tunnels, where
>> the tunnel socket is created by the kernel rather than being created
>> by userspace. This means L2TP tunnels and sessions can be created
>> manually, without needing an L2TP control protocol implemented in
>> userspace. This might be useful where the user wants a simple ethernet
>> over IP tunnel.
>>
>> A patch to iproute2 adds a new command set under "ip l2tp" to make use
>> of this feature. This will be submitted separately.
>>
>> Signed-off-by: James Chapman <[email-masked]>
>> Reviewed-by: Randy Dunlap <[email-masked]>
>> ---
>>  net/l2tp/l2tp_core.c    |  111 +++++++++++++++++++++++++++++++++++++++++++----
>>  net/l2tp/l2tp_core.h    |    7 +++
>>  net/l2tp/l2tp_netlink.c |   18 ++++++--
>>  3 files changed, 122 insertions(+), 14 deletions(-)
>>
>> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
>> index c08c859..1431b39 100644
>> --- a/net/l2tp/l2tp_core.c
>> +++ b/net/l2tp/l2tp_core.c
>> @@ -1259,6 +1259,78 @@ void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
>>  }
>>  EXPORT_SYMBOL_GPL(l2tp_tunnel_free);
>>  
>> +/* Create a socket for the tunnel, if one isn't set up by
>> + * userspace. This is used for static tunnels where there is no
>> + * managing L2TP daemon.
>> + */
>> +static int l2tp_tunnel_sock_create(u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct socket **sockp)
>> +{
>> +	int err = -EINVAL;
>> +	struct sockaddr_in udp_addr;
>> +	struct sockaddr_l2tpip ip_addr;
>> +	struct socket *sock;
>> +
>> +	switch (cfg->encap) {
>> +	case L2TP_ENCAPTYPE_UDP:
>> +		err = sock_create(AF_INET, SOCK_DGRAM, 0, sockp);
>> +		if (err < 0)
>> +			goto out;
>> +
>> +		sock = *sockp;
>> +
>> +		memset(&udp_addr, 0, sizeof(udp_addr));
>> +		udp_addr.sin_family = AF_INET;
>> +		udp_addr.sin_addr = cfg->local_ip;
>> +		udp_addr.sin_port = htons(cfg->local_udp_port);
>> +		err = kernel_bind(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr));
>> +		if (err < 0)
>> +			goto out;
>> +
> 
> I cant see how you use cfg->use_udp_checksums, something like : ?
> 
> 	if (!cfg->use_udp_checksums)
> 		sk->sk_no_check = UDP_CSUM_NOXMIT;

Good point. I forgot to add control of UDP checksums for the kernel
socket case. Thanks!

> 
>> +		udp_addr.sin_family = AF_INET;
>> +		udp_addr.sin_addr = cfg->peer_ip;
>> +		udp_addr.sin_port = htons(cfg->peer_udp_port);
>> +		err = kernel_connect(sock, (struct sockaddr *) &udp_addr, sizeof(udp_addr), 0);
>> +		if (err < 0)
>> +			goto out;
>> +
>> +		break;
>> +	case L2TP_ENCAPTYPE_IP:
>> +		err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_L2TP, sockp);
>> +		if (err < 0)
>> +			goto out;
>> +
>> +		sock = *sockp;
>> +
>> +		memset(&ip_addr, 0, sizeof(ip_addr));
>> +		ip_addr.l2tp_family = AF_INET;
>> +		ip_addr.l2tp_addr = cfg->local_ip;
>> +		ip_addr.l2tp_conn_id = tunnel_id;
>> +		err = kernel_bind(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr));
>> +		if (err < 0)
>> +			goto out;
>> +
>> +		ip_addr.l2tp_family = AF_INET;
>> +		ip_addr.l2tp_addr = cfg->peer_ip;
>> +		ip_addr.l2tp_conn_id = peer_tunnel_id;
>> +		err = kernel_connect(sock, (struct sockaddr *) &ip_addr, sizeof(ip_addr), 0);
>> +		if (err < 0)
>> +			goto out;
>> +
>> +		break;
>> +
>> +	default:
>> +		goto out;
>> +	}
>> +
>> +out:
>> +	if ((err < 0) && sock) {
>> +		sock_release(sock);
>> +		*sockp = NULL;
>> +	}
>> +
>> +	return err;
>> +}
>> +
>>  int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg, struct l2tp_tunnel **tunnelp)
>>  {
>>  	struct l2tp_tunnel *tunnel = NULL;
>> @@ -1269,14 +1341,21 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
>>  	enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
>>  
>>  	/* Get the tunnel socket from the fd, which was opened by
>> -	 * the userspace L2TP daemon.
>> +	 * the userspace L2TP daemon. If not specified, create a
>> +	 * kernel socket.
>>  	 */
>> -	err = -EBADF;
>> -	sock = sockfd_lookup(fd, &err);
>> -	if (!sock) {
>> -		printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
>> -		       tunnel_id, fd, err);
>> -		goto err;
>> +	if (fd < 0) {
>> +		err = l2tp_tunnel_sock_create(tunnel_id, peer_tunnel_id, cfg, &sock);
>> +		if (err < 0)
>> +			goto err;
>> +	} else {
>> +		err = -EBADF;
>> +		sock = sockfd_lookup(fd, &err);
>> +		if (!sock) {
>> +			printk(KERN_ERR "tunl %hu: sockfd_lookup(fd=%d) returned %d\n",
>> +			       tunnel_id, fd, err);
>> +			goto err;
>> +		}
>>  	}
>>  
>>  	sk = sock->sk;
>> @@ -1369,7 +1448,10 @@ err:
>>  	if (tunnelp)
>>  		*tunnelp = tunnel;
>>  
>> -	if (sock)
>> +	/* If tunnel's socket was created by the kernel, it doesn't
>> +	 *  have a file.
>> +	 */
>> +	if (sock && sock->file)
>>  		sockfd_put(sock);
>>  
>>  	return err;
>> @@ -1381,13 +1463,22 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
>>  int l2tp_tunnel_delete(struct l2tp_tunnel *tunnel)
>>  {
>>  	int err = 0;
>> +	struct socket *sock = tunnel->sock ? tunnel->sock->sk_socket : NULL;
>>  
>>  	/* Force the tunnel socket to close. This will eventually
>>  	 * cause the tunnel to be deleted via the normal socket close
>>  	 * mechanisms when userspace closes the tunnel socket.
>>  	 */
>> -	if ((tunnel->sock != NULL) && (tunnel->sock->sk_socket != NULL))
>> -		err = inet_shutdown(tunnel->sock->sk_socket, 2);
>> +	if (sock != NULL) {
>> +		err = inet_shutdown(sock, 2);
>> +
>> +		/* If the tunnel's socket was created by the kernel,
>> +		 * close the socket here since the socket was not
>> +		 * created by userspace.
>> +		 */
>> +		if (sock->file == NULL)
>> +			err = inet_release(sock);
>> +	}
>>  
>>  	return err;
>>  }
>> diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
>> index c5f2cc9..7e3387b 100644
>> --- a/net/l2tp/l2tp_core.h
>> +++ b/net/l2tp/l2tp_core.h
>> @@ -146,6 +146,13 @@ struct l2tp_tunnel_cfg {
>>  	int			debug;		/* bitmask of debug message
>>  						 * categories */
>>  	enum l2tp_encap_type	encap;
>> +
>> +	/* Used only for kernel-created sockets */
>> +	struct in_addr		local_ip;
>> +	struct in_addr		peer_ip;
>> +	u16			local_udp_port;
>> +	u16			peer_udp_port;
>> +	int			use_udp_checksums:1;
>>  };
>>  
>>  struct l2tp_tunnel {
>> diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
>> index e051c13..115ea01 100644
>> --- a/net/l2tp/l2tp_netlink.c
>> +++ b/net/l2tp/l2tp_netlink.c
>> @@ -129,11 +129,21 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
>>  	}
>>  	cfg.encap = nla_get_u16(info->attrs[L2TP_ATTR_ENCAP_TYPE]);
>>  
>> -	if (!info->attrs[L2TP_ATTR_FD]) {
>> -		ret = -EINVAL;
>> -		goto out;
>> +	fd = -1;
>> +	if (info->attrs[L2TP_ATTR_FD]) {
>> +		fd = nla_get_u32(info->attrs[L2TP_ATTR_FD]);
>> +	} else {
>> +		if (info->attrs[L2TP_ATTR_IP_SADDR])
>> +			cfg.local_ip.s_addr = nla_get_be32(info->attrs[L2TP_ATTR_IP_SADDR]);
>> +		if (info->attrs[L2TP_ATTR_IP_DADDR])
>> +			cfg.peer_ip.s_addr = nla_get_be32(info->attrs[L2TP_ATTR_IP_DADDR]);
>> +		if (info->attrs[L2TP_ATTR_UDP_SPORT])
>> +			cfg.local_udp_port = nla_get_u16(info->attrs[L2TP_ATTR_UDP_SPORT]);
>> +		if (info->attrs[L2TP_ATTR_UDP_DPORT])
>> +			cfg.peer_udp_port = nla_get_u16(info->attrs[L2TP_ATTR_UDP_DPORT]);
>> +		if (info->attrs[L2TP_ATTR_UDP_CSUM])
>> +			cfg.use_udp_checksums = nla_get_flag(info->attrs[L2TP_ATTR_UDP_CSUM]);
>>  	}
>> -	fd = nla_get_u32(info->attrs[L2TP_ATTR_FD]);
>>  
>>  	if (info->attrs[L2TP_ATTR_DEBUG])
>>  		cfg.debug = nla_get_u32(info->attrs[L2TP_ATTR_DEBUG]);
>>
> 
> 
> 

-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development