diff options
| author | David Ahern <dsahern@gmail.com> | 2018-05-21 09:08:13 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-05-22 10:51:09 +0200 |
| commit | 50d889b1789458d1f7d7f40ff4f628b670047773 (patch) | |
| tree | b135cefd3c0de7c3ff7fb6729b8e36235bdea92f /net/ipv4 | |
| parent | fd0bfa8d6e046237cb591bd3b51c87c56d4772b2 (diff) | |
net/ipv4: Add helper to return path MTU based on fib result
Determine path MTU from a FIB lookup result. Logic is a distillation of
ip_dst_mtu_maybe_forward.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/route.c | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 29268efad247..ac3b22bc51b2 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1352,6 +1352,37 @@ static struct fib_nh_exception *find_exception(struct fib_nh *nh, __be32 daddr) return NULL; } +/* MTU selection: + * 1. mtu on route is locked - use it + * 2. mtu from nexthop exception + * 3. mtu from egress device + */ + +u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr) +{ + struct fib_info *fi = res->fi; + struct fib_nh *nh = &fi->fib_nh[res->nh_sel]; + struct net_device *dev = nh->nh_dev; + u32 mtu = 0; + + if (dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu || + fi->fib_metrics->metrics[RTAX_LOCK - 1] & (1 << RTAX_MTU)) + mtu = fi->fib_mtu; + + if (likely(!mtu)) { + struct fib_nh_exception *fnhe; + + fnhe = find_exception(nh, daddr); + if (fnhe && !time_after_eq(jiffies, fnhe->fnhe_expires)) + mtu = fnhe->fnhe_pmtu; + } + + if (likely(!mtu)) + mtu = min(READ_ONCE(dev->mtu), IP_MAX_MTU); + + return mtu - lwtunnel_headroom(nh->nh_lwtstate, mtu); +} + static bool rt_bind_exception(struct rtable *rt, struct fib_nh_exception *fnhe, __be32 daddr, const bool do_cache) { |