batman-adv/patches/0052-batman-adv-mcast-fix-duplicate-mcast-packets-in-BLA-.patch

   1 From: Linus Lüssing <linus.luessing@c0d3.blue>
   2 Date: Tue, 15 Sep 2020 09:54:08 +0200
   3 Subject: batman-adv: mcast: fix duplicate mcast packets in BLA backbone from LAN
   4
   5 Scenario:
   6 * Multicast frame send from a BLA backbone (multiple nodes with
   7   their bat0 bridged together, with BLA enabled)
   8
   9 Issue:
  10 * BLA backbone nodes receive the frame multiple times on bat0
  11
  12 For multicast frames received via batman-adv broadcast packets the
  13 originator of the broadcast packet is checked before decapsulating and
  14 forwarding the frame to bat0 (batadv_bla_is_backbone_gw()->
  15 batadv_recv_bcast_packet()). If it came from a node which shares the
  16 same BLA backbone with us then it is not forwarded to bat0 to avoid a
  17 loop.
  18
  19 When sending a multicast frame in a non-4-address batman-adv unicast
  20 packet we are currently missing this check - and cannot do so because
  21 the batman-adv unicast packet has no originator address field.
  22
  23 However, we can simply fix this on the sender side by only sending the
  24 multicast frame via unicasts to interested nodes which do not share the
  25 same BLA backbone with us. This also nicely avoids some unnecessary
  26 transmissions on mesh side.
  27
  28 Note that no infinite loop was observed, probably because of dropping
  29 via batadv_interface_tx()->batadv_bla_tx(). However the duplicates still
  30 utterly confuse switches/bridges, ICMPv6 duplicate address detection and
  31 neighbor discovery and therefore leads to long delays before being able
  32 to establish TCP connections, for instance. And it also leads to the Linux
  33 bridge printing messages like:
  34 "br-lan: received packet on eth1 with own address as source address ..."
  35
  36 Fixes: 405cc1e5a81e ("batman-adv: Modified forwarding behaviour for multicast packets")
  37 Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
  38 Acked-by: Simon Wunderlich <sw@simonwunderlich.de>
  39 Signed-off-by: Sven Eckelmann <sven@narfation.org>
  40
  41 Origin: backport, https://git.open-mesh.org/batman-adv.git/commit/3c39a2455a5be02ecceeaf1a15976bddd611392e
  42
  43 diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
  44 index 39640d3d6fbdf8244344db6e79f2d769eb0972d9..764c304ffa5f6dc976050fa6b6f6e0891981c4f4 100644
  45 --- a/net/batman-adv/multicast.c
  46 +++ b/net/batman-adv/multicast.c
  47 @@ -62,10 +62,12 @@
  48  #include <uapi/linux/batadv_packet.h>
  49  #include <uapi/linux/batman_adv.h>
  50
  51 +#include "bridge_loop_avoidance.h"
  52  #include "hard-interface.h"
  53  #include "hash.h"
  54  #include "log.h"
  55  #include "netlink.h"
  56 +#include "send.h"
  57  #include "soft-interface.h"
  58  #include "translation-table.h"
  59  #include "tvlv.h"
  60 @@ -1027,6 +1029,35 @@ batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
  61         }
  62  }
  63
  64 +/**
  65 + * batadv_mcast_forw_send_orig() - send a multicast packet to an originator
  66 + * @bat_priv: the bat priv with all the soft interface information
  67 + * @skb: the multicast packet to send
  68 + * @vid: the vlan identifier
  69 + * @orig_node: the originator to send the packet to
  70 + *
  71 + * Return: NET_XMIT_DROP in case of error or NET_XMIT_SUCCESS otherwise.
  72 + */
  73 +int batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
  74 +                               struct sk_buff *skb,
  75 +                               unsigned short vid,
  76 +                               struct batadv_orig_node *orig_node)
  77 +{
  78 +       /* Avoid sending multicast-in-unicast packets to other BLA
  79 +        * gateways - they already got the frame from the LAN side
  80 +        * we share with them.
  81 +        * TODO: Refactor to take BLA into account earlier, to avoid
  82 +        * reducing the mcast_fanout count.
  83 +        */
  84 +       if (batadv_bla_is_backbone_gw_orig(bat_priv, orig_node->orig, vid)) {
  85 +               dev_kfree_skb(skb);
  86 +               return NET_XMIT_SUCCESS;
  87 +       }
  88 +
  89 +       return batadv_send_skb_unicast(bat_priv, skb, BATADV_UNICAST, 0,
  90 +                                      orig_node, vid);
  91 +}
  92 +
  93  /**
  94   * batadv_mcast_want_unsnoop_update() - update unsnoop counter and list
  95   * @bat_priv: the bat priv with all the soft interface information
  96 diff --git a/net/batman-adv/multicast.h b/net/batman-adv/multicast.h
  97 index 3b04ab13f0eb1044454315c04e75a22ce4351afd..6f9f3813fc59a8e8798b71297c8d8f9ef50b5e72 100644
  98 --- a/net/batman-adv/multicast.h
  99 +++ b/net/batman-adv/multicast.h
 100 @@ -51,6 +51,11 @@ enum batadv_forw_mode
 101  batadv_mcast_forw_mode(struct batadv_priv *bat_priv, struct sk_buff *skb,
 102                        struct batadv_orig_node **mcast_single_orig);
 103
 104 +int batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
 105 +                               struct sk_buff *skb,
 106 +                               unsigned short vid,
 107 +                               struct batadv_orig_node *orig_node);
 108 +
 109  void batadv_mcast_init(struct batadv_priv *bat_priv);
 110
 111  int batadv_mcast_flags_seq_print_text(struct seq_file *seq, void *offset);
 112 @@ -78,6 +83,16 @@ static inline int batadv_mcast_init(struct batadv_priv *bat_priv)
 113         return 0;
 114  }
 115
 116 +static inline int
 117 +batadv_mcast_forw_send_orig(struct batadv_priv *bat_priv,
 118 +                           struct sk_buff *skb,
 119 +                           unsigned short vid,
 120 +                           struct batadv_orig_node *orig_node)
 121 +{
 122 +       kfree_skb(skb);
 123 +       return NET_XMIT_DROP;
 124 +}
 125 +
 126  static inline int
 127  batadv_mcast_mesh_info_put(struct sk_buff *msg, struct batadv_priv *bat_priv)
 128  {
 129 diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
 130 index 97e28907a0acbb3d64d8ceebf7b1df13dc396300..267f6e6c802f1a7d3eb41a0f3aa2142ca3b21414 100644
 131 --- a/net/batman-adv/soft-interface.c
 132 +++ b/net/batman-adv/soft-interface.c
 133 @@ -367,9 +367,8 @@ static int batadv_interface_tx(struct sk_buff *skb,
 134                                 goto dropped;
 135                         ret = batadv_send_skb_via_gw(bat_priv, skb, vid);
 136                 } else if (mcast_single_orig) {
 137 -                       ret = batadv_send_skb_unicast(bat_priv, skb,
 138 -                                                     BATADV_UNICAST, 0,
 139 -                                                     mcast_single_orig, vid);
 140 +                       ret = batadv_mcast_forw_send_orig(bat_priv, skb, vid,
 141 +                                                         mcast_single_orig);
 142                 } else {
 143                         if (batadv_dat_snoop_outgoing_arp_request(bat_priv,
 144                                                                   skb))