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Date: Tue, 15 Dec 2015 12:26:46 -0800
From: Tom Herbert <tom@...bertland.com>
To: Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc: Linux Kernel Network Developers <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net 2/2] udp: restrict offloads to one namespace
On Tue, Dec 15, 2015 at 12:01 PM, Hannes Frederic Sowa
<hannes@...essinduktion.org> wrote:
> udp tunnel offloads tend to aggregate datagrams based on inner
> headers. gro engine gets notified by tunnel implementations about
> possible offloads. The match is solely based on the port number.
>
> Imagine a tunnel bound to port 53, the offloading will look into all
> DNS packets and tries to aggregate them based on the inner data found
> within. This could lead to data corruption and malformed DNS packets.
>
> While this patch minimizes the problem and helps an administrator to find
> the issue by querying ip tunnel/fou, a better way would be to match on
> the specific destination ip address so if a user space socket is bound
> to the same address it will conflict.
>
I don't know... seems like this is more likely to add code into the
critical path rather than solve a problem impacting anyone yet. No
other GRO code needs to be namespace aware and none of these fancy HW
offloads for UDP encapsulations are going to care anything about
namespaces.
I think you point out the real underlying problem though, the UDP
offloads are restricted only be done by destination port and nothing
else. A more flexible method would be to allow matching on based
addresses, four tuples, interfaces etc. (latter may be needed to
offload connected UDP).
Tom
> Cc: Tom Herbert <tom@...bertland.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
> ---
> drivers/net/geneve.c | 2 +-
> drivers/net/vxlan.c | 2 +-
> include/net/protocol.h | 2 +-
> net/ipv4/fou.c | 2 +-
> net/ipv4/udp_offload.c | 10 +++++++---
> 5 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
> index c2b79f5d1c89b6..b70ce46a5e7040 100644
> --- a/drivers/net/geneve.c
> +++ b/drivers/net/geneve.c
> @@ -376,7 +376,7 @@ static void geneve_notify_add_rx_port(struct geneve_sock *gs)
> int err;
>
> if (sa_family == AF_INET) {
> - err = udp_add_offload(&gs->udp_offloads);
> + err = udp_add_offload(sock_net(sk), &gs->udp_offloads);
> if (err)
> pr_warn("geneve: udp_add_offload failed with status %d\n",
> err);
> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
> index ba363cedef8082..2428175c4dd4bb 100644
> --- a/drivers/net/vxlan.c
> +++ b/drivers/net/vxlan.c
> @@ -621,7 +621,7 @@ static void vxlan_notify_add_rx_port(struct vxlan_sock *vs)
> int err;
>
> if (sa_family == AF_INET) {
> - err = udp_add_offload(&vs->udp_offloads);
> + err = udp_add_offload(net, &vs->udp_offloads);
> if (err)
> pr_warn("vxlan: udp_add_offload failed with status %d\n", err);
> }
> diff --git a/include/net/protocol.h b/include/net/protocol.h
> index d6fcc1fcdb5b09..da689f5432dee2 100644
> --- a/include/net/protocol.h
> +++ b/include/net/protocol.h
> @@ -107,7 +107,7 @@ int inet_del_offload(const struct net_offload *prot, unsigned char num);
> void inet_register_protosw(struct inet_protosw *p);
> void inet_unregister_protosw(struct inet_protosw *p);
>
> -int udp_add_offload(struct udp_offload *prot);
> +int udp_add_offload(struct net *net, struct udp_offload *prot);
> void udp_del_offload(struct udp_offload *prot);
>
> #if IS_ENABLED(CONFIG_IPV6)
> diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
> index bd903fe0f7508d..976f0dcf699197 100644
> --- a/net/ipv4/fou.c
> +++ b/net/ipv4/fou.c
> @@ -498,7 +498,7 @@ static int fou_create(struct net *net, struct fou_cfg *cfg,
> sk->sk_allocation = GFP_ATOMIC;
>
> if (cfg->udp_config.family == AF_INET) {
> - err = udp_add_offload(&fou->udp_offloads);
> + err = udp_add_offload(net, &fou->udp_offloads);
> if (err)
> goto error;
> }
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index f9386160cbee02..5d396b96ae8bb9 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -21,6 +21,7 @@ static struct udp_offload_priv __rcu *udp_offload_base __read_mostly;
>
> struct udp_offload_priv {
> struct udp_offload *offload;
> + possible_net_t net;
> struct rcu_head rcu;
> struct udp_offload_priv __rcu *next;
> };
> @@ -241,13 +242,14 @@ out:
> return segs;
> }
>
> -int udp_add_offload(struct udp_offload *uo)
> +int udp_add_offload(struct net *net, struct udp_offload *uo)
> {
> struct udp_offload_priv *new_offload = kzalloc(sizeof(*new_offload), GFP_ATOMIC);
>
> if (!new_offload)
> return -ENOMEM;
>
> + write_pnet(&new_offload->net, net);
> new_offload->offload = uo;
>
> spin_lock(&udp_offload_lock);
> @@ -311,7 +313,8 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
> rcu_read_lock();
> uo_priv = rcu_dereference(udp_offload_base);
> for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
> - if (uo_priv->offload->port == uh->dest &&
> + if (net_eq(read_pnet(&uo_priv->net), dev_net(skb->dev)) &&
> + uo_priv->offload->port == uh->dest &&
> uo_priv->offload->callbacks.gro_receive)
> goto unflush;
> }
> @@ -389,7 +392,8 @@ int udp_gro_complete(struct sk_buff *skb, int nhoff)
>
> uo_priv = rcu_dereference(udp_offload_base);
> for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
> - if (uo_priv->offload->port == uh->dest &&
> + if (net_eq(read_pnet(&uo_priv->net), dev_net(skb->dev)) &&
> + uo_priv->offload->port == uh->dest &&
> uo_priv->offload->callbacks.gro_complete)
> break;
> }
> --
> 2.5.0
>
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