aboutsummaryrefslogtreecommitdiffstats
path: root/net/ipv4/route.c
diff options
context:
space:
mode:
authorDavid Ahern <dsahern@gmail.com>2018-05-21 09:08:13 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2018-05-22 10:51:09 +0200
commit50d889b1789458d1f7d7f40ff4f628b670047773 (patch)
treeb135cefd3c0de7c3ff7fb6729b8e36235bdea92f /net/ipv4/route.c
parentMerge branch 'bpf-af-xdp-cleanups' (diff)
downloadlinux-dev-50d889b1789458d1f7d7f40ff4f628b670047773.tar.xz
linux-dev-50d889b1789458d1f7d7f40ff4f628b670047773.zip
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/route.c')
-rw-r--r--net/ipv4/route.c31
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)
{