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    Subject[PATCH 4.4 015/342] ipv6: enforce flowi6_oif usage in ip6_dst_lookup_tail()
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Paolo Abeni <pabeni@redhat.com>

    [ Upstream commit 6f21c96a78b835259546d8f3fb4edff0f651d478 ]

    The current implementation of ip6_dst_lookup_tail basically
    ignore the egress ifindex match: if the saddr is set,
    ip6_route_output() purposefully ignores flowi6_oif, due
    to the commit d46a9d678e4c ("net: ipv6: Dont add RT6_LOOKUP_F_IFACE
    flag if saddr set"), if the saddr is 'any' the first route lookup
    in ip6_dst_lookup_tail fails, but upon failure a second lookup will
    be performed with saddr set, thus ignoring the ifindex constraint.

    This commit adds an output route lookup function variant, which
    allows the caller to specify lookup flags, and modify
    ip6_dst_lookup_tail() to enforce the ifindex match on the second
    lookup via said helper.

    ip6_route_output() becames now a static inline function build on
    top of ip6_route_output_flags(); as a side effect, out-of-tree
    modules need now a GPL license to access the output route lookup
    functionality.

    Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Acked-by: David Ahern <dsa@cumulusnetworks.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    include/net/ip6_route.h | 12 ++++++++++--
    net/ipv6/ip6_output.c | 6 +++++-
    net/ipv6/route.c | 7 +++----
    3 files changed, 18 insertions(+), 7 deletions(-)

    --- a/include/net/ip6_route.h
    +++ b/include/net/ip6_route.h
    @@ -64,8 +64,16 @@ static inline bool rt6_need_strict(const

    void ip6_route_input(struct sk_buff *skb);

    -struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
    - struct flowi6 *fl6);
    +struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
    + struct flowi6 *fl6, int flags);
    +
    +static inline struct dst_entry *ip6_route_output(struct net *net,
    + const struct sock *sk,
    + struct flowi6 *fl6)
    +{
    + return ip6_route_output_flags(net, sk, fl6, 0);
    +}
    +
    struct dst_entry *ip6_route_lookup(struct net *net, struct flowi6 *fl6,
    int flags);

    --- a/net/ipv6/ip6_output.c
    +++ b/net/ipv6/ip6_output.c
    @@ -909,6 +909,7 @@ static int ip6_dst_lookup_tail(struct ne
    struct rt6_info *rt;
    #endif
    int err;
    + int flags = 0;

    /* The correct way to handle this would be to do
    * ip6_route_get_saddr, and then ip6_route_output; however,
    @@ -940,10 +941,13 @@ static int ip6_dst_lookup_tail(struct ne
    dst_release(*dst);
    *dst = NULL;
    }
    +
    + if (fl6->flowi6_oif)
    + flags |= RT6_LOOKUP_F_IFACE;
    }

    if (!*dst)
    - *dst = ip6_route_output(net, sk, fl6);
    + *dst = ip6_route_output_flags(net, sk, fl6, flags);

    err = (*dst)->error;
    if (err)
    --- a/net/ipv6/route.c
    +++ b/net/ipv6/route.c
    @@ -1174,11 +1174,10 @@ static struct rt6_info *ip6_pol_route_ou
    return ip6_pol_route(net, table, fl6->flowi6_oif, fl6, flags);
    }

    -struct dst_entry *ip6_route_output(struct net *net, const struct sock *sk,
    - struct flowi6 *fl6)
    +struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
    + struct flowi6 *fl6, int flags)
    {
    struct dst_entry *dst;
    - int flags = 0;
    bool any_src;

    dst = l3mdev_rt6_dst_by_oif(net, fl6);
    @@ -1199,7 +1198,7 @@ struct dst_entry *ip6_route_output(struc

    return fib6_rule_lookup(net, fl6, flags, ip6_pol_route_output);
    }
    -EXPORT_SYMBOL(ip6_route_output);
    +EXPORT_SYMBOL_GPL(ip6_route_output_flags);

    struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_orig)
    {
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