xfrm: remove the fragment check for ipv6 beet mode

stable inclusion
from stable-5.10.50
commit 6a56913355504ed772a11e129304f4c934a3c6ff
bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6a56913355504ed772a11e129304f4c934a3c6ff

--------------------------------

[ Upstream commit eebd49a4 ]

In commit 68dc022d ("xfrm: BEET mode doesn't support fragments
for inner packets"), it tried to fix the issue that in TX side the
packet is fragmented before the ESP encapping while in the RX side
the fragments always get reassembled before decapping with ESP.

This is not true for IPv6. IPv6 is different, and it's using exthdr
to save fragment info, as well as the ESP info. Exthdrs are added
in TX and processed in RX both in order. So in the above case, the
ESP decapping will be done earlier than the fragment reassembling
in TX side.

Here just remove the fragment check for the IPv6 inner packets to
recover the fragments support for BEET mode.

Fixes: 68dc022d ("xfrm: BEET mode doesn't support fragments for inner packets")
Reported-by: NXiumei Mu <xmu@redhat.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/xfrm/xfrm_output.c

@@ -711,15 +711,8 @@ static int xfrm6_tunnel_check_size(struct sk_buff *skb)
 static int xfrm6_extract_output(struct xfrm_state *x, struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_IPV6)
-	unsigned int ptr = 0;
 	int err;
 
-	if (x->outer_mode.encap == XFRM_MODE_BEET &&
-	    ipv6_find_hdr(skb, &ptr, NEXTHDR_FRAGMENT, NULL, NULL) >= 0) {
-		net_warn_ratelimited("BEET mode doesn't support inner IPv6 fragments\n");
-		return -EAFNOSUPPORT;
-	}
-
 	err = xfrm6_tunnel_check_size(skb);
 	if (err)
 		return err;