[PATCH net v2] gro: Make GRO aware of lightweight tunnels.

[Jesse Gross <jesse@kernel.org>]

GRO is currently not aware of tunnel metadata generated by lightweight
tunnels and stored in the dst. This leads to two possible problems:
 * Incorrectly merging two frames that have different metadata.
 * Leaking of allocated metadata from merged frames.

This avoids those problems by comparing the tunnel information before
merging, similar to how we handle other metadata (such as vlan tags),
and releasing any state when we are done.

Reported-by: John <john.phillips5@hpe.com>
Fixes: 2e15ea39 ("ip_gre: Add support to collect tunnel metadata.")
Signed-off-by: Jesse Gross <jesse@kernel.org>
---
v2: Remove branches to optimize for common case where there is no dst.
---
 include/net/dst_metadata.h | 18 ++++++++++++++++++
 net/core/dev.c             |  7 +++++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h
index 6816f0f..30a56ab 100644
--- a/include/net/dst_metadata.h
+++ b/include/net/dst_metadata.h
@@ -44,6 +44,24 @@ static inline bool skb_valid_dst(const struct sk_buff *skb)
 	return dst && !(dst->flags & DST_METADATA);
 }
 
+static inline int skb_metadata_dst_cmp(const struct sk_buff *skb_a,
+				       const struct sk_buff *skb_b)
+{
+	const struct metadata_dst *a, *b;
+
+	if (!(skb_a->_skb_refdst | skb_b->_skb_refdst))
+		return 0;
+
+	a = (const struct metadata_dst *) skb_dst(skb_a);
+	b = (const struct metadata_dst *) skb_dst(skb_b);
+
+	if (!a != !b || a->u.tun_info.options_len != b->u.tun_info.options_len)
+		return 1;
+
+	return memcmp(&a->u.tun_info, &b->u.tun_info,
+		      sizeof(a->u.tun_info) + a->u.tun_info.options_len);
+}
+
 struct metadata_dst *metadata_dst_alloc(u8 optslen, gfp_t flags);
 struct metadata_dst __percpu *metadata_dst_alloc_percpu(u8 optslen, gfp_t flags);
 
diff --git a/net/core/dev.c b/net/core/dev.c
index cc9e365..8cba3d8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4351,6 +4351,7 @@ static void gro_list_prepare(struct napi_struct *napi, struct sk_buff *skb)
 
 		diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
 		diffs |= p->vlan_tci ^ skb->vlan_tci;
+		diffs |= skb_metadata_dst_cmp(p, skb);
 		if (maclen == ETH_HLEN)
 			diffs |= compare_ether_header(skb_mac_header(p),
 						      skb_mac_header(skb));
@@ -4548,10 +4549,12 @@ static gro_result_t napi_skb_finish(gro_result_t ret, struct sk_buff *skb)
 		break;
 
 	case GRO_MERGED_FREE:
-		if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD)
+		if (NAPI_GRO_CB(skb)->free == NAPI_GRO_FREE_STOLEN_HEAD) {
+			skb_dst_drop(skb);
 			kmem_cache_free(skbuff_head_cache, skb);
-		else
+		} else {
 			__kfree_skb(skb);
+		}
 		break;
 
 	case GRO_HELD:
-- 
2.5.0