[PATCH iproute2 v2 6/9] l2tp: read IPv6 UDP checksum attributes from kernel

["Asbjørn Sloth Tønnesen" <asbjorn@asbjorn.st>]

In case of an older kernel that doesn't set L2TP_ATTR_UDP_ZERO_CSUM6_{RX,TX}
the old hard-coded value is being preserved, since the attribute flag will be
missing.

Signed-off-by: Asbjørn Sloth Tønnesen <asbjorn@asbjorn.st>
---
 ip/ipl2tp.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/ip/ipl2tp.c b/ip/ipl2tp.c
index 03ca0cc..f5d4113 100644
--- a/ip/ipl2tp.c
+++ b/ip/ipl2tp.c
@@ -292,12 +292,9 @@ static int get_response(struct nlmsghdr *n, void *arg)
 	if (attrs[L2TP_ATTR_UDP_CSUM])
 		p->udp_csum = !!rta_getattr_u8(attrs[L2TP_ATTR_UDP_CSUM]);
 
-	/*
-	 * Not fetching from L2TP_ATTR_UDP_ZERO_CSUM6_{T,R}X because the
-	 * kernel doesn't send it so just leave it as default value.
-	 */
-	p->udp6_csum_tx = 1;
-	p->udp6_csum_rx = 1;
+	p->udp6_csum_tx = !attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX];
+	p->udp6_csum_rx = !attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX];
+
 	if (attrs[L2TP_ATTR_COOKIE])
 		memcpy(p->cookie, RTA_DATA(attrs[L2TP_ATTR_COOKIE]),
 		       p->cookie_len = RTA_PAYLOAD(attrs[L2TP_ATTR_COOKIE]));
-- 
2.10.2