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authorLina Wang <lina.wang@mediatek.com>2022-02-26 10:48:01 +0300
committerSteffen Klassert <steffen.klassert@secunet.com>2022-03-01 14:08:40 +0300
commit4ff2980b6bd2aa6b4ded3ce3b7c0ccfab29980af (patch)
tree67fd950067dde9adfac616ad69ffb703f5c90b34 /net/xfrm
parent519ca6fa960587d02904a9f8f79d587ac874fb03 (diff)
downloadlinux-4ff2980b6bd2aa6b4ded3ce3b7c0ccfab29980af.tar.xz
xfrm: fix tunnel model fragmentation behavior
in tunnel mode, if outer interface(ipv4) is less, it is easily to let inner IPV6 mtu be less than 1280. If so, a Packet Too Big ICMPV6 message is received. When send again, packets are fragmentized with 1280, they are still rejected with ICMPV6(Packet Too Big) by xfrmi_xmit2(). According to RFC4213 Section3.2.2: if (IPv4 path MTU - 20) is less than 1280 if packet is larger than 1280 bytes Send ICMPv6 "packet too big" with MTU=1280 Drop packet else Encapsulate but do not set the Don't Fragment flag in the IPv4 header. The resulting IPv4 packet might be fragmented by the IPv4 layer on the encapsulator or by some router along the IPv4 path. endif else if packet is larger than (IPv4 path MTU - 20) Send ICMPv6 "packet too big" with MTU = (IPv4 path MTU - 20). Drop packet. else Encapsulate and set the Don't Fragment flag in the IPv4 header. endif endif Packets should be fragmentized with ipv4 outer interface, so change it. After it is fragemtized with ipv4, there will be double fragmenation. No.48 & No.51 are ipv6 fragment packets, No.48 is double fragmentized, then tunneled with IPv4(No.49& No.50), which obey spec. And received peer cannot decrypt it rightly. 48 2002::10 2002::11 1296(length) IPv6 fragment (off=0 more=y ident=0xa20da5bc nxt=50) 49 0x0000 (0) 2002::10 2002::11 1304 IPv6 fragment (off=0 more=y ident=0x7448042c nxt=44) 50 0x0000 (0) 2002::10 2002::11 200 ESP (SPI=0x00035000) 51 2002::10 2002::11 180 Echo (ping) request 52 0x56dc 2002::10 2002::11 248 IPv6 fragment (off=1232 more=n ident=0xa20da5bc nxt=50) xfrm6_noneed_fragment has fixed above issues. Finally, it acted like below: 1 0x6206 192.168.1.138 192.168.1.1 1316 Fragmented IP protocol (proto=Encap Security Payload 50, off=0, ID=6206) [Reassembled in #2] 2 0x6206 2002::10 2002::11 88 IPv6 fragment (off=0 more=y ident=0x1f440778 nxt=50) 3 0x0000 2002::10 2002::11 248 ICMPv6 Echo (ping) request Signed-off-by: Lina Wang <lina.wang@mediatek.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_interface.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index 4e3c62d1ad9e..1e8b26eecb3f 100644
--- a/net/xfrm/xfrm_interface.c
+++ b/net/xfrm/xfrm_interface.c
@@ -304,7 +304,10 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
if (mtu < IPV6_MIN_MTU)
mtu = IPV6_MIN_MTU;
- icmpv6_ndo_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+ if (skb->len > 1280)
+ icmpv6_ndo_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+ else
+ goto xmit;
} else {
if (!(ip_hdr(skb)->frag_off & htons(IP_DF)))
goto xmit;