netdev - [PATCH 3/3] vti6: Change minimum MTU to IPV4_MIN

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Message-ID: <20180507084323.22165-4-steffen.klassert@secunet.com>
Date:   Mon, 7 May 2018 10:43:23 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH 3/3] vti6: Change minimum MTU to IPV4_MIN_MTU, vti6 can carry IPv4 too

From: Stefano Brivio <sbrivio@...hat.com>

A vti6 interface can carry IPv4 as well, so it makes no sense to
enforce a minimum MTU of IPV6_MIN_MTU.

If the user sets an MTU below IPV6_MIN_MTU, IPv6 will be
disabled on the interface, courtesy of addrconf_notify().

Reported-by: Xin Long <lucien.xin@...il.com>
Fixes: b96f9afee4eb ("ipv4/6: use core net MTU range checking")
Fixes: c6741fbed6dc ("vti6: Properly adjust vti6 MTU from MTU of lower device")
Fixes: 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device")
Signed-off-by: Stefano Brivio <sbrivio@...hat.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
 net/ipv6/ip6_vti.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index c214ffec02f0..ca957dd93a29 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -669,7 +669,7 @@ static void vti6_link_config(struct ip6_tnl *t, bool keep_mtu)
 	else
 		mtu = ETH_DATA_LEN - LL_MAX_HEADER - sizeof(struct ipv6hdr);
 
-	dev->mtu = max_t(int, mtu, IPV6_MIN_MTU);
+	dev->mtu = max_t(int, mtu, IPV4_MIN_MTU);
 }
 
 /**
@@ -881,7 +881,7 @@ static void vti6_dev_setup(struct net_device *dev)
 	dev->priv_destructor = vti6_dev_free;
 
 	dev->type = ARPHRD_TUNNEL6;
-	dev->min_mtu = IPV6_MIN_MTU;
+	dev->min_mtu = IPV4_MIN_MTU;
 	dev->max_mtu = IP_MAX_MTU - sizeof(struct ipv6hdr);
 	dev->flags |= IFF_NOARP;
 	dev->addr_len = sizeof(struct in6_addr);
-- 
2.14.1