Since UDP-Lite is always using checksum, the following path is
triggered when calculating pseudo header for it:
udp4_csum_init() or udp6_csum_init()
skb_checksum_init_zero_check()
__skb_checksum_validate_complete()
The problem can appear if skb->len is less than CHECKSUM_BREAK. In
this particular case __skb_checksum_validate_complete() also invokes
__skb_checksum_complete(skb). If UDP-Lite is using partial checksum
that covers only part of a packet, the function will return bad
checksum and the packet will be dropped.
It can be fixed if we skip skb_checksum_init_zero_check() and only
set the required pseudo header checksum for UDP-Lite with partial
checksum before udp4_csum_init()/udp6_csum_init() functions return.
Fixes: ed70fcfcee95 ("net: Call skb_checksum_init in IPv4")
Fixes: e4f45b7f40bd ("net: Call skb_checksum_init in IPv6")
Signed-off-by: Alexey Kodanev <alexey.koda...@oracle.com>
---
Alternatively, we could modify skb_checksum_init_zero_check() because
it is used only in udp4_csum_init() and udp6_csum_init() as well as
introducing a new 'cscov' parameter in __skb_checksum_validate_complete()
and calling __skb_checksum_complete_head() if 'cscov' not equals zero.
But these changes would touch general code in skbuff.h
include/net/udplite.h | 1 +
net/ipv4/udp.c | 5 +++++
net/ipv6/ip6_checksum.c | 5 +++++
3 files changed, 11 insertions(+)
diff --git a/include/net/udplite.h b/include/net/udplite.h
index 81bdbf9..9185e45 100644
--- a/include/net/udplite.h
+++ b/include/net/udplite.h
@@ -64,6 +64,7 @@ static inline int udplite_checksum_init(struct sk_buff *skb,
struct udphdr *uh)
UDP_SKB_CB(skb)->cscov = cscov;
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->ip_summed = CHECKSUM_NONE;
+ skb->csum_valid = 0;
}
return 0;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index bfaefe5..e5ef7c3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2024,6 +2024,11 @@ static inline int udp4_csum_init(struct sk_buff *skb,
struct udphdr *uh,
err = udplite_checksum_init(skb, uh);
if (err)
return err;
+
+ if (UDP_SKB_CB(skb)->partial_cov) {
+ skb->csum = inet_compute_pseudo(skb, proto);
+ return 0;
+ }
}
/* Note, we are only interested in != 0 or == 0, thus the
diff --git a/net/ipv6/ip6_checksum.c b/net/ipv6/ip6_checksum.c
index ec43d18..547515e 100644
--- a/net/ipv6/ip6_checksum.c
+++ b/net/ipv6/ip6_checksum.c
@@ -73,6 +73,11 @@ int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh,
int proto)
err = udplite_checksum_init(skb, uh);
if (err)
return err;
+
+ if (UDP_SKB_CB(skb)->partial_cov) {
+ skb->csum = ip6_compute_pseudo(skb, proto);
+ return 0;
+ }
}
/* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)
--
1.8.3.1
