On 11/6/19 11:52 PM, Praveen Chaudhary wrote:
skb->csum is updated incorrectly, when manipulation for NF_NAT_MANIP_SRC\DST is done on IPV6 packet. Fix: No need to update skb->csum in function inet_proto_csum_replace16(), even if skb->ip_summed == CHECKSUM_COMPLETE, because change in L4 header checksum field and change in IPV6 header cancels each other for skb->csum calculation. Signed-off-by: Praveen Chaudhary <pchaudhary@xxxxxxxxxxxx> Signed-off-by: Zhenggen Xu <zxu@xxxxxxxxxxxx> Signed-off-by: Andy Stracner <astracner@xxxxxxxxxxxx> Reviewed-by: Florian Westphal <fw@xxxxxxxxx> --- Changes in V2. 1.) Updating diff as per email discussion with Florian Westphal. Since inet_proto_csum_replace16() does incorrect calculation for skb->csum in all cases. 2.) Change in Commmit logs. --- --- Changes in V3. Addressing Pablo`s Suggesion. 1.) Updated Subject and description 2.) Added full documentation of function. --- --- net/core/utils.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/net/core/utils.c b/net/core/utils.c index 6b6e51d..af3b5cb 100644 --- a/net/core/utils.c +++ b/net/core/utils.c @@ -438,6 +438,21 @@ void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb, } EXPORT_SYMBOL(inet_proto_csum_replace4);+/**+ * inet_proto_csum_replace16 - update L4 header checksum field as per the + * update in IPv6 Header. Note, there is no need to update skb->csum in this + * function, even if skb->ip_summed == CHECKSUM_COMPLETE, because change in L4 + * header checksum field and change in IPV6 header cancels each other for + * skb->csum calculation. + * + * @sum: L4 header checksum field + * @skb: sk_buff for the packet + * @from: old IPv6 address + * @to: new IPv6 address + * @pseudohdr: True if L4 header checksum includes pseudoheader + * + * Return void + */ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, const __be32 *from, const __be32 *to, bool pseudohdr) @@ -449,9 +464,6 @@ void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb, if (skb->ip_summed != CHECKSUM_PARTIAL) { *sum = csum_fold(csum_partial(diff, sizeof(diff), ~csum_unfold(*sum))); - if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr) - skb->csum = ~csum_partial(diff, sizeof(diff), - ~skb->csum);
What is the technical rationale in removing this here but not in any of the other inet_proto_csum_replace*() functions? You changelog has zero analysis on why here but not elsewhere this change would be needed?
} else if (pseudohdr) *sum = ~csum_fold(csum_partial(diff, sizeof(diff), csum_unfold(*sum)));
