[2/4] batman-adv: Speed up dat by snooping received ip traffic

  From cc88159dcf18f4b8310414d2d71635fad76bf5bb Mon Sep 17 00:00:00 2001
From: Andreas Pape <apape@phoenixcontact.com>
Date: Fri, 12 Feb 2016 11:03:10 +0100
Subject: [PATCH 2/4] batman-adv: Speed up dat by snooping received ip
traffic

This patch shall speed up dat by snooping all incoming ip traffic instead
of only relying on ARP handling. This shall especially increase the
probability
that a gateway into a backbone network already has a fitting dat entry to
answer
incoming arp requests directly coming from the backbone network.

Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/distributed-arp-table.c |   18 ++++++++++++++++++
 net/batman-adv/distributed-arp-table.h |    8 +++++++-
 net/batman-adv/soft-interface.c        |   21 ++++++++++++++++++++-
 3 files changed, 45 insertions(+), 2 deletions(-)


@@ -412,11 +414,28 @@ void batadv_interface_rx(struct net_device
*soft_iface,
        ethhdr = eth_hdr(skb);

        switch (ntohs(ethhdr->h_proto)) {
+       case ETH_P_IP:
+               iphdr = (struct iphdr *)(skb->data + ETH_HLEN);
+               /* snoop incoming traffic for dat update using the source
mac
+                * and source ip to speed up dat.
+                * Question: does this break the fundamental idea of
dat????
+                */
+               batadv_dat_entry_check(bat_priv, iphdr->saddr,
ethhdr->h_source, vid);
+               break;
        case ETH_P_8021Q:
                vhdr = (struct vlan_ethhdr *)skb->data;

-               if (vhdr->h_vlan_encapsulated_proto != ethertype)
+               if (vhdr->h_vlan_encapsulated_proto != ethertype) {
+                       /* snoop incoming traffic for dat update also for
vlan
+                        * tagged frames.
+                        * Question: does this break the fundamental idea
of dat????
+                        */
+                       if (vhdr->h_vlan_encapsulated_proto == ETH_P_IP) {
+                               iphdr = (struct iphdr *)(vhdr +
sizeof(struct vlan_ethhdr));
+                               batadv_dat_entry_check(bat_priv,
iphdr->saddr, vhdr->h_source, vid);
+                       }
                        break;
+               }

                /* fall through */
        case ETH_P_BATMAN:
--
1.7.0.4



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck
  

On Friday 12 February 2016 14:52:34 Andreas Pape wrote:
> From cc88159dcf18f4b8310414d2d71635fad76bf5bb Mon Sep 17 00:00:00 2001
> From: Andreas Pape <apape@phoenixcontact.com>
> Date: Fri, 12 Feb 2016 11:03:10 +0100
> Subject: [PATCH 2/4] batman-adv: Speed up dat by snooping received ip
> traffic
> 
> This patch shall speed up dat by snooping all incoming ip traffic instead
> of only relying on ARP handling. This shall especially increase the
> probability
> that a gateway into a backbone network already has a fitting dat entry to
> answer
> incoming arp requests directly coming from the backbone network.
> 
> Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
> ---
>  net/batman-adv/distributed-arp-table.c |   18 ++++++++++++++++++
>  net/batman-adv/distributed-arp-table.h |    8 +++++++-
>  net/batman-adv/soft-interface.c        |   21 ++++++++++++++++++++-
>  3 files changed, 45 insertions(+), 2 deletions(-)
> 
> diff --git a/net/batman-adv/distributed-arp-table.c
> b/net/batman-adv/distributed-arp-table.c
> index 93893bf..4e64e6c 100644
> --- a/net/batman-adv/distributed-arp-table.c
> +++ b/net/batman-adv/distributed-arp-table.c
> @@ -362,6 +362,24 @@ out:
>                 batadv_dat_entry_put(dat_entry);
>  }
> 
> +/**
> + * batadv_dat_entry_check - check and update a dat entry
> + * @bat_priv: the bat priv with all the soft interface information
> + * @ip: ipv4 to add/edit
> + * @mac_addr: mac address to assign to the given ipv4
> + * @vid: VLAN identifier
> + *
> + * checks additionally, if dat is enabled. can be called from other
> modules.
> + */
> +void batadv_dat_entry_check(struct batadv_priv *bat_priv, __be32 ip,
> +                                u8 *mac_addr, unsigned short vid)
> +{
> +       if(!atomic_read(&bat_priv->distributed_arp_table))
> +               return;
> +
> +       batadv_dat_entry_add(bat_priv, ip, mac_addr, vid);
> +}
> +
>  #ifdef CONFIG_BATMAN_ADV_DEBUG
> 
>  /**
> diff --git a/net/batman-adv/distributed-arp-table.h
> b/net/batman-adv/distributed-arp-table.h
> index 813ecea..a2ab16b 100644
> --- a/net/batman-adv/distributed-arp-table.h
> +++ b/net/batman-adv/distributed-arp-table.h
> @@ -80,7 +80,8 @@ batadv_dat_init_own_addr(struct batadv_priv *bat_priv,
>  int batadv_dat_init(struct batadv_priv *bat_priv);
>  void batadv_dat_free(struct batadv_priv *bat_priv);
>  int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset);
> -
> +void batadv_dat_entry_check(struct batadv_priv *bat_priv, __be32 ip,
> +                                u8 *mac_addr, unsigned short vid);
>  /**
>   * batadv_dat_inc_counter - increment the correct DAT packet counter
>   * @bat_priv: the bat priv with all the soft interface information
> @@ -173,6 +174,11 @@ static inline void batadv_dat_inc_counter(struct
> batadv_priv *bat_priv,
>  {
>  }
> 
> +void batadv_dat_entry_check(struct batadv_priv *bat_priv, __be32 ip,
> +                                u8 *mac_addr, unsigned short vid)
> +{
> +}
> +
>  #endif /* CONFIG_BATMAN_ADV_DAT */
> 
>  #endif /* _NET_BATMAN_ADV_DISTRIBUTED_ARP_TABLE_H_ */
> diff --git a/net/batman-adv/soft-interface.c
> b/net/batman-adv/soft-interface.c
> index 0710379..41d7987 100644
> --- a/net/batman-adv/soft-interface.c
> +++ b/net/batman-adv/soft-interface.c
> @@ -28,6 +28,7 @@
>  #include <linux/fs.h>
>  #include <linux/if_ether.h>
>  #include <linux/if_vlan.h>
> +#include <linux/ip.h>
>  #include <linux/jiffies.h>
>  #include <linux/kernel.h>
>  #include <linux/kref.h>
> @@ -390,6 +391,7 @@ void batadv_interface_rx(struct net_device
> *soft_iface,
>         __be16 ethertype = htons(ETH_P_BATMAN);
>         struct vlan_ethhdr *vhdr;
>         struct ethhdr *ethhdr;
> +       struct iphdr *iphdr;
>         unsigned short vid;
>         bool is_bcast;
> 
> @@ -412,11 +414,28 @@ void batadv_interface_rx(struct net_device
> *soft_iface,
>         ethhdr = eth_hdr(skb);
> 
>         switch (ntohs(ethhdr->h_proto)) {
> +       case ETH_P_IP:
> +               iphdr = (struct iphdr *)(skb->data + ETH_HLEN);
> +               /* snoop incoming traffic for dat update using the source
> mac
> +                * and source ip to speed up dat.
> +                * Question: does this break the fundamental idea of
> dat????
> +                */

That is a really good question, although it doesn't belong in the code ;)

@Antonio, CC'ing you since this is more a design question/proposal and you may 
have thought about this yet.

Basically, doing this change means that we will put a lot of IP addresses in 
our cache which are not in our local network - typically, all Internet IP 
addresses along with the gateway backbone. Also these addresses will never be 
requested by ARP and are therefore practically just littering our cache. They 
are purged after 5 minutes so the impact may be reasonable, but still ...

Maybe there is a way to limit the entries to local networks? Also (and in 
general), should we have an upper limit how many entries we store in DAT? 
After applying this patch, doing a subnet ping scan can deplete the RAM in 
small routers I'm afraid. :)

(even now, that would be possible with fake ARP replies I guess)

Also, why don't you check the ip destination as well while at it?

Cheers,
      Simon
  

> > @@ -412,11 +414,28 @@ void batadv_interface_rx(struct net_device
> > *soft_iface,
> >         ethhdr = eth_hdr(skb);
> >
> >         switch (ntohs(ethhdr->h_proto)) {
> > +       case ETH_P_IP:
> > +               iphdr = (struct iphdr *)(skb->data + ETH_HLEN);
> > +               /* snoop incoming traffic for dat update using the
source
> > mac
> > +                * and source ip to speed up dat.
> > +                * Question: does this break the fundamental idea of
> > dat????
> > +                */
>
> That is a really good question, although it doesn't belong in the code
;)
>

I know, but I was myself unsure if this is a good idea and wanted to
provoke a discussion about this ;-)

> @Antonio, CC'ing you since this is more a design question/proposal
> and you may
> have thought about this yet.
>
> Basically, doing this change means that we will put a lot of IP
addresses in
> our cache which are not in our local network - typically, all Internet
IP
> addresses along with the gateway backbone. Also these addresses
willnever be
> requested by ARP and are therefore practically just littering our cache.
They
> are purged after 5 minutes so the impact may be reasonable, but still
...
>

I agree that performance and especially consumption of RAM is an issue
here
depending on the network size....

> Maybe there is a way to limit the entries to local networks? Also (and
in
> general), should we have an upper limit how many entries we store in
DAT?
> After applying this patch, doing a subnet ping scan can deplete the RAM
in
> small routers I'm afraid. :)
>
> (even now, that would be possible with fake ARP replies I guess)
>
> Also, why don't you check the ip destination as well while at it?
>
I only tried to check the source addresses with the gateways of a bla
setup
in mind. The goal was to increase the possiblity that already the gateway
can
answer the arp request. In this case only the traffic traveling from mesh
to
backbone is relevant. One could also snoop destination addresse for
traffic from
backbone to mesh, but do you think that this adds an extra benefit of
addtional
information except risking another decrease in forwarding performance ?

> Cheers,
>       Simon
Kind regards,
Andreas



..................................................................
PHOENIX CONTACT ELECTRONICS GmbH

Sitz der Gesellschaft / registered office of the company: 31812 Bad Pyrmont
USt-Id-Nr.: DE811742156
Amtsgericht Hannover HRB 100528 / district court Hannover HRB 100528
Geschäftsführer / Executive Board: Roland Bent, Dr. Martin Heubeck