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Date: Wed, 8 Jan 2014 23:09:19 -0800
From: Tom Herbert <therbert@...gle.com>
To: Or Gerlitz <ogerlitz@...lanox.com>
Cc: Jerry Chu <hkchu@...gle.com>, Eric Dumazet <edumazet@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Linux Netdev List <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>,
Yan Burman <yanb@...lanox.com>,
Shlomo Pongratz <shlomop@...lanox.com>
Subject: Re: [PATCH net-next V3 1/3] net: Add GRO support for UDP
encapsulating protocols
On Wed, Jan 8, 2014 at 12:34 PM, Or Gerlitz <ogerlitz@...lanox.com> wrote:
> Add GRO handlers for protocols that do UDP encapsulation, with the intent of
> being able to coalesce packets which encapsulate packets belonging to
> the same TCP session.
>
> For GRO purposes, the destination UDP port takes the role of the ether type
> field in the ethernet header or the next protocol in the IP header.
>
> The UDP GRO handler will only attempt to coalesce packets whose destination
> port is registered to have gro handler.
>
> Signed-off-by: Or Gerlitz <ogerlitz@...lanox.com>
> ---
> include/linux/netdevice.h | 10 +++-
> include/net/protocol.h | 3 +
> net/core/dev.c | 1 +
> net/ipv4/udp_offload.c | 129 +++++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 142 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index a2a70cc..360551a 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1652,7 +1652,9 @@ struct napi_gro_cb {
> unsigned long age;
>
> /* Used in ipv6_gro_receive() */
> - int proto;
> + u16 proto;
> +
> + u16 udp_mark;
>
> /* used to support CHECKSUM_COMPLETE for tunneling protocols */
> __wsum csum;
> @@ -1691,6 +1693,12 @@ struct packet_offload {
> struct list_head list;
> };
>
> +struct udp_offload {
> + __be16 port;
> + struct offload_callbacks callbacks;
> + struct list_head list;
> +};
> +
> /* often modified stats are per cpu, other are shared (netdev->stats) */
> struct pcpu_sw_netstats {
> u64 rx_packets;
> diff --git a/include/net/protocol.h b/include/net/protocol.h
> index fbf7676..fe9af94 100644
> --- a/include/net/protocol.h
> +++ b/include/net/protocol.h
> @@ -103,6 +103,9 @@ 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);
>
> +void udp_add_offload(struct udp_offload *prot);
> +void udp_del_offload(struct udp_offload *prot);
> +
> #if IS_ENABLED(CONFIG_IPV6)
> int inet6_add_protocol(const struct inet6_protocol *prot, unsigned char num);
> int inet6_del_protocol(const struct inet6_protocol *prot, unsigned char num);
> diff --git a/net/core/dev.c b/net/core/dev.c
> index ce01847..11f7acf 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3858,6 +3858,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
> NAPI_GRO_CB(skb)->same_flow = 0;
> NAPI_GRO_CB(skb)->flush = 0;
> NAPI_GRO_CB(skb)->free = 0;
> + NAPI_GRO_CB(skb)->udp_mark = 0;
>
> pp = ptype->callbacks.gro_receive(&napi->gro_list, skb);
> break;
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 79c62bd..2846ade 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -13,6 +13,16 @@
> #include <linux/skbuff.h>
> #include <net/udp.h>
> #include <net/protocol.h>
> +/*
> +struct udp_offload {
> + __be16 port;
> + struct offload_callbacks callbacks;
> + struct list_head list;
> +};
> +*/
> +
> +static DEFINE_SPINLOCK(udp_offload_lock);
> +static struct list_head udp_offload_base __read_mostly;
>
> static int udp4_ufo_send_check(struct sk_buff *skb)
> {
> @@ -89,14 +99,133 @@ out:
> return segs;
> }
>
> +void udp_add_offload(struct udp_offload *uo)
> +{
> + struct list_head *head = &udp_offload_base;
> +
> + spin_lock(&udp_offload_lock);
> + list_add_rcu(&uo->list, head);
> + spin_unlock(&udp_offload_lock);
> +}
> +EXPORT_SYMBOL(udp_add_offload);
> +
> +void udp_del_offload(struct udp_offload *uo)
> +{
> + struct list_head *head = &udp_offload_base;
> + struct udp_offload *uo1;
> +
> + spin_lock(&udp_offload_lock);
> + list_for_each_entry(uo1, head, list) {
> + if (uo == uo1) {
> + list_del_rcu(&uo->list);
> + goto out;
> + }
> + }
> +
> + pr_warn("udp_remove_offload: %p not found port %d\n", uo, htons(uo->port));
> +out:
> + spin_unlock(&udp_offload_lock);
> +
> + synchronize_net();
> +}
> +EXPORT_SYMBOL(udp_del_offload);
> +
> +static struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
> +{
> + struct list_head *ohead = &udp_offload_base;
> + struct udp_offload *poffload;
> + struct sk_buff *p, **pp = NULL;
> + struct udphdr *uh, *uh2;
> + unsigned int hlen, off;
> + int flush = 1;
> +
> + if (NAPI_GRO_CB(skb)->udp_mark ||
> + (!skb->encapsulation && skb->ip_summed != CHECKSUM_COMPLETE))
> + goto out;
> +
> + /* mark that this skb passed once through the udp gro layer */
> + NAPI_GRO_CB(skb)->udp_mark = 1;
> +
> + off = skb_gro_offset(skb);
> + hlen = off + sizeof(*uh);
> + uh = skb_gro_header_fast(skb, off);
> + if (skb_gro_header_hard(skb, hlen)) {
> + uh = skb_gro_header_slow(skb, hlen, off);
> + if (unlikely(!uh))
> + goto out;
> + }
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(poffload, ohead, list) {
> + if (poffload->port != uh->dest || !poffload->callbacks.gro_receive)
> + continue;
> + break;
> + }
> +
> + if (&poffload->list == ohead)
> + goto out_unlock;
> +
> + flush = 0;
> +
> + for (p = *head; p; p = p->next) {
> + if (!NAPI_GRO_CB(p)->same_flow)
> + continue;
> +
> + uh2 = (struct udphdr *)(p->data + off);
> + if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
> + NAPI_GRO_CB(p)->same_flow = 0;
> + continue;
> + }
> + goto found;
I don't believe this is correct. If you exit on the first match, skb's
that follow in the list can still be marked as same_flow. You need to
walk the whole list I believe (just get rid of the goto).
> + }
> +
> +found:
> + skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
> + pp = poffload->callbacks.gro_receive(head, skb);
> +
> +out_unlock:
> + rcu_read_unlock();
> +out:
> + NAPI_GRO_CB(skb)->flush |= flush;
> +
> + return pp;
> +}
> +
> +static int udp_gro_complete(struct sk_buff *skb, int nhoff)
> +{
> + struct list_head *ohead = &udp_offload_base;
> + struct udp_offload *poffload;
> + __be16 newlen = htons(skb->len - nhoff);
> + struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
> + int err = -ENOSYS;
> +
> + uh->len = newlen;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(poffload, ohead, list) {
> + if (poffload->port != uh->dest || !poffload->callbacks.gro_complete)
> + continue;
> + break;
> + }
> +
> + if (&poffload->list != ohead)
> + err = poffload->callbacks.gro_complete(skb, nhoff + sizeof(struct udphdr));
> +
> + rcu_read_unlock();
> + return err;
> +}
> +
> static const struct net_offload udpv4_offload = {
> .callbacks = {
> .gso_send_check = udp4_ufo_send_check,
> .gso_segment = udp4_ufo_fragment,
> + .gro_receive = udp_gro_receive,
> + .gro_complete = udp_gro_complete,
> },
> };
>
> int __init udpv4_offload_init(void)
> {
> + INIT_LIST_HEAD(&udp_offload_base);
> return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
> }
> --
> 1.7.1
>
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