Re: [RFC] Inverse of flowi{4,6}_oif: flowi{4,6}_not_oif

[David Ahern]

On 2/3/16 7:27 AM, Jason A. Donenfeld wrote:
FYI, for v4 at least, it's ridiculously easy and simple to implement:
=~=~=~=~=~=~=~=~=

diff --git a/include/net/flow.h b/include/net/flow.h
index 83969ee..29967ad 100644
--- a/include/net/flow.h
+++ b/include/net/flow.h
@@ -26,6 +26,7 @@ struct flowi_tunnel {

  struct flowi_common {
   int flowic_oif;
+ int flowic_not_oif;
   int flowic_iif;
   __u32 flowic_mark;
   __u8 flowic_tos;

I was going to suggest a flag:

@@ -36,6 +36,7 @@ struct flowi_common {
 #define FLOWI_FLAG_KNOWN_NH            0x02
 #define FLOWI_FLAG_L3MDEV_SRC          0x04
 #define FLOWI_FLAG_SKIP_NH_OIF         0x08
+#define FLOWI_FLAG_NOT_OIF             0x10
        __u32   flowic_secid;
        struct flowi_tunnel flowic_tun_key;
 };


but there are a number of oif checks that would have to be enhanced with 
the flag check. Adding a flowic_not_oif member is certainly simpler and 
there is a 4-byte hole in the struct.

@@ -67,6 +68,7 @@ union flowi_uli {
  struct flowi4 {
   struct flowi_common __fl_common;
  #define flowi4_oif  __fl_common.flowic_oif
+#define flowi4_not_oif  __fl_common.flowic_not_oif
  #define flowi4_iif  __fl_common.flowic_iif
  #define flowi4_mark  __fl_common.flowic_mark
  #define flowi4_tos  __fl_common.flowic_tos
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 7aea0cc..d03e991 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1429,6 +1429,8 @@ found:
          flp->flowi4_oif != nh->nh_oif)
       continue;
     }
+   if (flp->flowi4_not_oif && flp->flowi4_not_oif == nh->nh_oif)
+    continue;

     if (!(fib_flags & FIB_LOOKUP_NOREF))
      atomic_inc(&fi->fib_clntref);


For IPv6 start with ip6_pol_route_lookup and modifying rt6_device_match