Date:   Sat, 16 Mar 2019 19:11:07 +0200 (EET)
From:   Julian Anastasov <ja@....bg>
To:     Jacky Hu <hengqing.hu@...il.com>
cc:     jacky.hu@...mart.com, jason.niesz@...mart.com,
        Wensong Zhang <wensong@...ux-vs.org>,
        Simon Horman <horms@...ge.net.au>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        lvs-devel@...r.kernel.org, linux-kernel@...r.kernel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org
Subject: Re: [PATCH v3] ipvs: allow tunneling with gue encapsulation


	Hello,

On Sat, 16 Mar 2019, Jacky Hu wrote:

> ipip packets are blocked in some public cloud environments, this patch
> allows gue encapsulation with the tunneling method, which would make
> tunneling working in those environments.
> 
> Signed-off-by: Jacky Hu <hengqing.hu@...il.com>
> ---
>  include/net/ip_vs.h             |  5 ++
>  include/uapi/linux/ip_vs.h      | 17 ++++++
>  net/netfilter/ipvs/ip_vs_ctl.c  | 20 ++++++-
>  net/netfilter/ipvs/ip_vs_xmit.c | 93 +++++++++++++++++++++++++++++++--
>  4 files changed, 130 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index a0d2e0bb9a94..56c1770b00fe 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -603,6 +603,9 @@ struct ip_vs_dest_user_kern {
>  
>  	/* Address family of addr */
>  	u16			af;
> +
> +	u16			tun_type;	/* tunnel type */
> +	__be16			tun_port;	/* tunnel port */
>  };
>  
>  
> @@ -663,6 +666,8 @@ struct ip_vs_dest {
>  	atomic_t		conn_flags;	/* flags to copy to conn */
>  	atomic_t		weight;		/* server weight */
>  	atomic_t		last_weight;	/* server latest weight */
> +	atomic_t		tun_type;	/* tunnel type */
> +	atomic_t		tun_port;	/* tunnel port */
>  
>  	refcount_t		refcnt;		/* reference counter */
>  	struct ip_vs_stats      stats;          /* statistics */
> diff --git a/include/uapi/linux/ip_vs.h b/include/uapi/linux/ip_vs.h
> index 1c916b2f89dc..b43297691337 100644
> --- a/include/uapi/linux/ip_vs.h
> +++ b/include/uapi/linux/ip_vs.h
> @@ -124,6 +124,13 @@
>  
>  #define IP_VS_PEDATA_MAXLEN     255
>  
> +/* Tunnel types */
> +enum {
> +	IP_VS_CONN_F_TUNNEL_TYPE_IPIP = 0,	/* IPIP */
> +	IP_VS_CONN_F_TUNNEL_TYPE_GUE,		/* GUE */
> +	IP_VS_CONN_F_TUNNEL_TYPE_MAX,
> +};
> +
>  /*
>   *	The struct ip_vs_service_user and struct ip_vs_dest_user are
>   *	used to set IPVS rules through setsockopt.
> @@ -155,6 +162,9 @@ struct ip_vs_dest_user {
>  	/* thresholds for active connections */
>  	__u32		u_threshold;	/* upper threshold */
>  	__u32		l_threshold;	/* lower threshold */
> +
> +	__u16		tun_type;	/* tunnel type */
> +	__be16		tun_port;	/* tunnel port */

	The struct ip_vs_dest_user can not be changed anymore, it is
for the old setsockopt interface, for the new netlink interface we
extend only struct ip_vs_dest_user_kern which is not visible to
user space.

>  };
>  
>  
> @@ -220,6 +230,9 @@ struct ip_vs_dest_entry {
>  	__u32		u_threshold;	/* upper threshold */
>  	__u32		l_threshold;	/* lower threshold */
>  
> +	__u16		tun_type;	/* tunnel type */
> +	__be16		tun_port;	/* tunnel port */
> +

	Same for struct ip_vs_dest_entry, we can not change it

>  	__u32		activeconns;	/* active connections */
>  	__u32		inactconns;	/* inactive connections */
>  	__u32		persistconns;	/* persistent connections */
> @@ -392,6 +405,10 @@ enum {
>  
>  	IPVS_DEST_ATTR_STATS64,		/* nested attribute for dest stats */
>  
> +	IPVS_DEST_ATTR_TUN_TYPE,	/* tunnel type */
> +
> +	IPVS_DEST_ATTR_TUN_PORT,	/* tunnel port */
> +
>  	__IPVS_DEST_ATTR_MAX,
>  };
>  
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 432141f04af3..48509b03a5ea 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -830,6 +830,10 @@ __ip_vs_update_dest(struct ip_vs_service *svc, struct ip_vs_dest *dest,
>  	conn_flags = udest->conn_flags & IP_VS_CONN_F_DEST_MASK;
>  	conn_flags |= IP_VS_CONN_F_INACTIVE;
>  
> +	/* set the tunnel info */
> +	atomic_set(&dest->tun_type, udest->tun_type);
> +	atomic_set(&dest->tun_port, udest->tun_port);
> +
>  	/* set the IP_VS_CONN_F_NOOUTPUT flag if not masquerading/NAT */
>  	if ((conn_flags & IP_VS_CONN_F_FWD_MASK) != IP_VS_CONN_F_MASQ) {
>  		conn_flags |= IP_VS_CONN_F_NOOUTPUT;
> @@ -2869,6 +2873,8 @@ static const struct nla_policy ip_vs_dest_policy[IPVS_DEST_ATTR_MAX + 1] = {
>  	[IPVS_DEST_ATTR_PERSIST_CONNS]	= { .type = NLA_U32 },
>  	[IPVS_DEST_ATTR_STATS]		= { .type = NLA_NESTED },
>  	[IPVS_DEST_ATTR_ADDR_FAMILY]	= { .type = NLA_U16 },
> +	[IPVS_DEST_ATTR_TUN_TYPE]	= { .type = NLA_U8 },
> +	[IPVS_DEST_ATTR_TUN_PORT]	= { .type = NLA_U16 },
>  };
>  
>  static int ip_vs_genl_fill_stats(struct sk_buff *skb, int container_type,
> @@ -3172,6 +3178,10 @@ static int ip_vs_genl_fill_dest(struct sk_buff *skb, struct ip_vs_dest *dest)
>  			 IP_VS_CONN_F_FWD_MASK)) ||
>  	    nla_put_u32(skb, IPVS_DEST_ATTR_WEIGHT,
>  			atomic_read(&dest->weight)) ||
> +	    nla_put_u8(skb, IPVS_DEST_ATTR_TUN_TYPE,
> +		       atomic_read(&dest->tun_type)) ||
> +	    nla_put_u16(skb, IPVS_DEST_ATTR_TUN_PORT,
> +			atomic_read(&dest->tun_port)) ||

	nla_put_be16 for port

>  	    nla_put_u32(skb, IPVS_DEST_ATTR_U_THRESH, dest->u_threshold) ||
>  	    nla_put_u32(skb, IPVS_DEST_ATTR_L_THRESH, dest->l_threshold) ||
>  	    nla_put_u32(skb, IPVS_DEST_ATTR_ACTIVE_CONNS,
> @@ -3294,12 +3304,14 @@ static int ip_vs_genl_parse_dest(struct ip_vs_dest_user_kern *udest,
>  	/* If a full entry was requested, check for the additional fields */
>  	if (full_entry) {
>  		struct nlattr *nla_fwd, *nla_weight, *nla_u_thresh,
> -			      *nla_l_thresh;
> +			      *nla_l_thresh, *nla_tun_type, *nla_tun_port;
>  
>  		nla_fwd		= attrs[IPVS_DEST_ATTR_FWD_METHOD];
>  		nla_weight	= attrs[IPVS_DEST_ATTR_WEIGHT];
>  		nla_u_thresh	= attrs[IPVS_DEST_ATTR_U_THRESH];
>  		nla_l_thresh	= attrs[IPVS_DEST_ATTR_L_THRESH];
> +		nla_tun_type	= attrs[IPVS_DEST_ATTR_TUN_TYPE];
> +		nla_tun_port	= attrs[IPVS_DEST_ATTR_TUN_PORT];
>  
>  		if (!(nla_fwd && nla_weight && nla_u_thresh && nla_l_thresh))
>  			return -EINVAL;
> @@ -3309,6 +3321,12 @@ static int ip_vs_genl_parse_dest(struct ip_vs_dest_user_kern *udest,
>  		udest->weight = nla_get_u32(nla_weight);
>  		udest->u_threshold = nla_get_u32(nla_u_thresh);
>  		udest->l_threshold = nla_get_u32(nla_l_thresh);
> +
> +		if (nla_tun_type)
> +			udest->tun_type = nla_get_u8(nla_tun_type);
> +
> +		if (nla_tun_port)
> +			udest->tun_port = nla_get_u16(nla_tun_port);

	nla_get_be16 for port

>  	}
>  
>  	return 0;
> diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
> index 473cce2a5231..e748c5605b04 100644
> --- a/net/netfilter/ipvs/ip_vs_xmit.c
> +++ b/net/netfilter/ipvs/ip_vs_xmit.c
> @@ -32,6 +32,7 @@
>  #include <linux/slab.h>
>  #include <linux/tcp.h>                  /* for tcphdr */
>  #include <net/ip.h>
> +#include <net/gue.h>
>  #include <net/tcp.h>                    /* for csum_tcpudp_magic */
>  #include <net/udp.h>
>  #include <net/icmp.h>                   /* for icmp_send */
> @@ -989,6 +990,42 @@ static inline int __tun_gso_type_mask(int encaps_af, int orig_af)
>  	}
>  }
>  
> +static int
> +__build_gue_header(struct net *net, struct sk_buff *skb,
> +		   struct ip_vs_conn *cp, __u8 *next_protocol)
> +{
> +	__be16 dport;
> +	__be16 sport;
> +	struct udphdr  *udph;	/* Our new UDP header */
> +	struct guehdr  *gueh;	/* Our new GUE header */
> +
> +	skb_push(skb, sizeof(struct guehdr));
> +
> +	gueh = (struct guehdr *)skb->data;
> +
> +	gueh->control = 0;
> +	gueh->version = 0;
> +	gueh->hlen = 0;
> +	gueh->flags = 0;
> +	gueh->proto_ctype = *next_protocol;
> +
> +	skb_push(skb, sizeof(struct udphdr));
> +	skb_reset_transport_header(skb);
> +
> +	udph = udp_hdr(skb);
> +
> +	dport = htons(atomic_read(&cp->dest->tun_port));
> +	sport = udp_flow_src_port(net, skb, 0, 0, false);

	udp_flow_src_port should be called before pushing new headers,
eg. move it above:

	__be16 sport = udp_flow_src_port(net, skb, 0, 0, false);

> +	udph->dest = dport;
> +	udph->source = sport;
> +	udph->len = htons(skb->len);
> +	udph->check = 0;

	For udph->check there can be an additional patch/feature:

- we can add options for checksums, for example:

	--tun-nocsum: uh->check = 0, SKB_GSO_UDP_TUNNEL
		No checksum
		default

	--tun-csum:
		Checksum
		SKB_GSO_UDP_TUNNEL_CSUM
		udp_set_csum/udp6_set_csum as in fou_build_udp() and
		fou6_build_udp()

	--tun-remcsum:
		Remote Checksum Offload
		SKB_GSO_UDP_TUNNEL_CSUM | SKB_GSO_TUNNEL_REMCSUM
		udp_set_csum/udp6_set_csum
		like net/ipv4/fou.c:__gue_build_header() REMCSUM handling

	But for now check = 0 should be fine.

> +
> +	*next_protocol = IPPROTO_UDP;
> +
> +	return 0;
> +}
> +
>  /*
>   *   IP Tunneling transmitter
>   *
> @@ -1025,6 +1062,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
>  	struct iphdr  *iph;			/* Our new IP header */
>  	unsigned int max_headroom;		/* The extra header space needed */
>  	int ret, local;
> +	int tun_type, gso_type;
>  
>  	EnterFunction(10);
>  
> @@ -1033,7 +1071,7 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
>  				   IP_VS_RT_MODE_NON_LOCAL |
>  				   IP_VS_RT_MODE_CONNECT |
>  				   IP_VS_RT_MODE_TUNNEL, &saddr, ipvsh);
> -	if (local < 0)
> +	if (!cp->dest || local < 0)

	May be this cp->dest check can be moved to  __ip_vs_get_out_rt()
and __ip_vs_get_out_rt_v6() because we need to account the added header 
when calculating mtu and also because it should not stop the traffic when
local = true:

	mtu = dst_mtu(&rt->dst) - sizeof(struct iphdr);

	add:
	if (!dest)
		goto err_put;
	switch (atomic_read(&dest->tun_type)) {
	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
		mtu -= sizeof(struct udphdr) + sizeof(struct guehdr);
		break;
	default:
		break;
	}

>  		goto tx_error;
>  	if (local)
>  		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
> @@ -1046,6 +1084,14 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
>  	 */
>  	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
>  
> +	tun_type = atomic_read(&cp->dest->tun_type);
> +
> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		max_headroom += sizeof(struct udphdr) + sizeof(struct guehdr);
> +		break;
> +	}
> +
>  	/* We only care about the df field if sysctl_pmtu_disc(ipvs) is set */
>  	dfp = sysctl_pmtu_disc(ipvs) ? &df : NULL;
>  	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
> @@ -1054,11 +1100,26 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
>  	if (IS_ERR(skb))
>  		goto tx_error;
>  
> -	if (iptunnel_handle_offloads(skb, __tun_gso_type_mask(AF_INET, cp->af)))
> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		gso_type = SKB_GSO_UDP_TUNNEL;
> +		break;
> +	default:
> +		gso_type = __tun_gso_type_mask(AF_INET, cp->af);
> +		break;
> +	}
> +
> +	if (iptunnel_handle_offloads(skb, gso_type))
>  		goto tx_error;
>  
>  	skb->transport_header = skb->network_header;
>  

	We should call skb_set_inner_ipproto(skb, next_protocol) to
properly segment the skb in skb_udp_tunnel_segment(), after
iptunnel_handle_offloads and before it is changed by __build_gue_header
from IPPROTO_IPIP/IPPROTO_IPV6 to UDP.

> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		__build_gue_header(dev_net(tdev), skb, cp, &next_protocol);

	Use net instead of dev_net(tdev)

> +		break;
> +	}
> +
>  	skb_push(skb, sizeof(struct iphdr));
>  	skb_reset_network_header(skb);
>  	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
> @@ -1112,6 +1173,7 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
>  	struct ipv6hdr  *iph;		/* Our new IP header */
>  	unsigned int max_headroom;	/* The extra header space needed */
>  	int ret, local;
> +	int tun_type, gso_type;
>  
>  	EnterFunction(10);
>  
> @@ -1121,7 +1183,7 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
>  				      IP_VS_RT_MODE_LOCAL |
>  				      IP_VS_RT_MODE_NON_LOCAL |
>  				      IP_VS_RT_MODE_TUNNEL);
> -	if (local < 0)
> +	if (!cp->dest || local < 0)

	Above dest check will be moved before the mtu check

>  		goto tx_error;
>  	if (local)
>  		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
> @@ -1134,17 +1196,40 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
>  	 */
>  	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct ipv6hdr);
>  
> +	tun_type = atomic_read(&cp->dest->tun_type);
> +
> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		max_headroom += sizeof(struct udphdr) + sizeof(struct guehdr);
> +		break;
> +	}
> +
>  	skb = ip_vs_prepare_tunneled_skb(skb, cp->af, max_headroom,
>  					 &next_protocol, &payload_len,
>  					 &dsfield, &ttl, NULL);
>  	if (IS_ERR(skb))
>  		goto tx_error;
>  
> -	if (iptunnel_handle_offloads(skb, __tun_gso_type_mask(AF_INET6, cp->af)))
> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		gso_type = SKB_GSO_UDP_TUNNEL;
> +		break;
> +	default:
> +		gso_type = __tun_gso_type_mask(AF_INET, cp->af);

	For IPv6 use AF_INET6

> +		break;
> +	}
> +
> +	if (iptunnel_handle_offloads(skb, gso_type))
>  		goto tx_error;
>  
>  	skb->transport_header = skb->network_header;
>  

	skb_set_inner_ipproto(skb, next_protocol);

> +	switch (tun_type) {
> +	case IP_VS_CONN_F_TUNNEL_TYPE_GUE:
> +		__build_gue_header(dev_net(tdev), skb, cp, &next_protocol);

	Use net instead of dev_net(tdev)

> +		break;
> +	}
> +
>  	skb_push(skb, sizeof(struct ipv6hdr));
>  	skb_reset_network_header(skb);
>  	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
> -- 

	Also:

- just for correctness we can set udest->tun_type to
	IP_VS_CONN_F_TUNNEL_TYPE_IPIP in ip_vs_copy_udest_compat()

- __build_gue_header: can be named ipvs_gue_encap because we add 2 headers

- ip_vs_add_dest() and ip_vs_edit_dest() can return EINVAL when
GUE comes with port 0.

	As for ipvsadm v2 patch, I'll comment it again when we stabilize
the kernel patch but for now few comments:

- there are missing switch-case breaks

- for FMT_TUN_INFO in print_title it would be enough to show only this:
-> RemoteAddress:Port Forward TunnelInfo":

- in print_service_entry() better to use func to print 
tunnames[e->tun_type] in case the kernel returns something ipvsadm
does not support yet

- libipvs/ip_vs.h: struct ip_vs_dest_kern: can not be changed

- libipvs/ip_vs.h: struct ip_vs_dest_entry_kern: can not be changed

Regards

--
Julian Anastasov <ja@....bg>

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