From: dsahern@kernel.org
To: netdev@vger.kernel.org, borkmann@iogearbox.net, ast@kernel.org
Cc: davem@davemloft.net, David Ahern <dsahern@gmail.com>
Subject: [PATCH v2 bpf-next 1/3] net/ipv4: Add helper to return path MTU based on fib result
Date: Mon, 21 May 2018 09:08:13 -0700 [thread overview]
Message-ID: <20180521160816.7060-2-dsahern@kernel.org> (raw)
In-Reply-To: <20180521160816.7060-1-dsahern@kernel.org>
From: David Ahern <dsahern@gmail.com>
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>
---
include/net/ip_fib.h | 2 ++
net/ipv4/route.c | 31 +++++++++++++++++++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 81d0f2107ff1..69c91d1934c1 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -449,4 +449,6 @@ static inline void fib_proc_exit(struct net *net)
}
#endif
+u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr);
+
#endif /* _NET_FIB_H */
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)
{
--
2.11.0
next prev parent reply other threads:[~2018-05-21 16:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-21 16:08 [PATCH v2 bpf-next 0/3] bpf: Add MTU check to fib lookup helper dsahern
2018-05-21 16:08 ` dsahern [this message]
2018-05-21 16:08 ` [PATCH v2 bpf-next 2/3] net/ipv6: Add helper to return path MTU based on fib result dsahern
2018-05-21 16:08 ` [PATCH v2 bpf-next 3/3] bpf: Add mtu checking to FIB forwarding helper dsahern
2018-05-22 8:59 ` [PATCH v2 bpf-next 0/3] bpf: Add MTU check to fib lookup helper Daniel Borkmann
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