ipv4/GRO: Make GRO conform to RFC 6864
RFC 6864 states that the IPv4 ID field MUST NOT be used for purposes other
than fragmentation and reassembly. Currently we are looking at this field
as a way of identifying what frames can be aggregated and which cannot for
GRO. While this is valid for frames that do not have DF set, it is invalid
to do so if the bit is set.
In addition we were generating IPv4 ID collisions when 2 or more flows were
interleaved over the same tunnel. To prevent that we store the result of
all IP ID checks via a "|=" instead of overwriting previous values.
Change-Id: I96d90494f929fb217ceaa1698213465b0a17835a
CRs-Fixed: 2221952
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Patch-mainline: netdev @ April 1, 2016, 6:05 p.m
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Signed-off-by: Manjunathappa Prakash <prakashpm@codeaurora.org>
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 83ac5da..90c91a7 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1385,14 +1385,23 @@
(iph->tos ^ iph2->tos) |
((iph->frag_off ^ iph2->frag_off) & htons(IP_DF));
- /* Save the IP ID check to be included later when we get to
- * the transport layer so only the inner most IP ID is checked.
- * This is because some GSO/TSO implementations do not
- * correctly increment the IP ID for the outer hdrs.
- */
- NAPI_GRO_CB(p)->flush_id =
- ((u16)(ntohs(iph2->id) + NAPI_GRO_CB(p)->count) ^ id);
NAPI_GRO_CB(p)->flush |= flush;
+
+ /* For non-atomic datagrams we need to save the IP ID offset
+ * to be included later. If the frame has the DF bit set
+ * we must ignore the IP ID value as per RFC 6864.
+ */
+ if (iph2->frag_off & htons(IP_DF))
+ continue;
+
+ /* We must save the offset as it is possible to have multiple
+ * flows using the same protocol and address pairs so we
+ * need to wait until we can validate this is part of the
+ * same flow with a 5-tuple or better to avoid unnecessary
+ * collisions between flows.
+ */
+ NAPI_GRO_CB(p)->flush_id |= ntohs(iph2->id) ^
+ (u16)(id - NAPI_GRO_CB(p)->count);
}
NAPI_GRO_CB(skb)->flush |= flush;