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SubjectRe: [net-next 1/2] Perform IPv4 FIB lookup in a predefined FIB table
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On 2/12/20 6:09 PM, Carmine Scarpitta wrote:
> In IPv4, the routing subsystem is invoked by calling ip_route_input_rcu()
> which performs the recognition logic and calls ip_route_input_slow().
>
> ip_route_input_slow() initialises both "fi" and "table" members
> of the fib_result structure to null before calling fib_lookup().
>
> fib_lookup() performs fib lookup in the routing table configured
> by the policy routing rules.
>
> In this patch, we allow invoking the ip4 routing subsystem
> with known routing table. This is useful for use-cases implementing
> a separate routing table per tenant.
>
> The patch introduces a new flag named "tbl_known" to the definition of
> ip_route_input_rcu() and ip_route_input_slow().
>
> When the flag is set, ip_route_input_slow() will call fib_table_lookup()
> using the defined table instead of using fib_lookup().

I do not like this change. If you want a specific table lookup, then why
just call fib_table_lookup directly? Both it and rt_dst_alloc are
exported for modules. Your next patch already does a fib table lookup.


>
> Signed-off-by: Carmine Scarpitta <carmine.scarpitta@uniroma2.it>
> Acked-by: Ahmed Abdelsalam <ahmed.abdelsalam@gssi.it>
> Acked-by: Andrea Mayer <andrea.mayer@uniroma2.it>
> Acked-by: Paolo Lungaroni <paolo.lungaroni@cnit.it>
> ---
> include/net/route.h | 2 +-
> net/ipv4/route.c | 22 ++++++++++++++--------
> 2 files changed, 15 insertions(+), 9 deletions(-)
>
> diff --git a/include/net/route.h b/include/net/route.h
> index a9c60fc68e36..4ff977bd7029 100644
> --- a/include/net/route.h
> +++ b/include/net/route.h
> @@ -183,7 +183,7 @@ int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 src,
> u8 tos, struct net_device *devin);
> int ip_route_input_rcu(struct sk_buff *skb, __be32 dst, __be32 src,
> u8 tos, struct net_device *devin,
> - struct fib_result *res);
> + struct fib_result *res, bool tbl_known);
>
> int ip_route_use_hint(struct sk_buff *skb, __be32 dst, __be32 src,
> u8 tos, struct net_device *devin,
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index d5c57b3f77d5..39cec9883d6f 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2077,7 +2077,7 @@ int ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
>
> static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
> u8 tos, struct net_device *dev,
> - struct fib_result *res)
> + struct fib_result *res, bool tbl_known)
> {
> struct in_device *in_dev = __in_dev_get_rcu(dev);
> struct flow_keys *flkeys = NULL, _flkeys;
> @@ -2109,8 +2109,6 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
> if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
> goto martian_source;
>
> - res->fi = NULL;
> - res->table = NULL;
> if (ipv4_is_lbcast(daddr) || (saddr == 0 && daddr == 0))
> goto brd_input;

I believe this also introduces a potential bug. You remove the fi
initialization yet do not cover the goto case.


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