is_skb_forwardable attempts to detect if a packet is too large to
be sent to the destination device. However, this test does not
consider GSO packets, and it is possible that a GSO packet, when
resegmented, will be larger than the device can transmit.
Add detection for packets which will be too large by creating a
skb_gso_validate_len() routine which is similar to
skb_gso_validate_mtu(), but which considers L2 headers, and wire
it up in is_skb_forwardable().
Signed-off-by: Daniel Axtens <d...@axtens.net>
---
include/linux/skbuff.h | 1 +
net/core/dev.c | 7 ++++---
net/core/skbuff.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b8acafd73272..6a9e4b6f80a7 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3287,6 +3287,7 @@ int skb_shift(struct sk_buff *tgt, struct sk_buff *skb,
int shiftlen);
void skb_scrub_packet(struct sk_buff *skb, bool xnet);
unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu);
+bool skb_gso_validate_len(const struct sk_buff *skb, unsigned int len);
struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
int skb_ensure_writable(struct sk_buff *skb, int write_len);
diff --git a/net/core/dev.c b/net/core/dev.c
index 94435cd09072..5af04be128c1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1841,11 +1841,12 @@ bool is_skb_forwardable(const struct net_device *dev,
const struct sk_buff *skb)
if (skb->len <= len)
return true;
- /* if TSO is enabled, we don't care about the length as the packet
- * could be forwarded without being segmented before
+ /*
+ * if TSO is enabled, we need to check the size of the
+ * segmented packets
*/
if (skb_is_gso(skb))
- return true;
+ return skb_gso_validate_len(skb, len);
return false;
}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 01e8285aea73..aefe049e4b0c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4945,6 +4945,40 @@ bool skb_gso_validate_mtu(const struct sk_buff *skb,
unsigned int mtu)
}
EXPORT_SYMBOL_GPL(skb_gso_validate_mtu);
+/**
+ * skb_gso_validate_len - Will a split GSO skb fit in a given length?
+ *
+ * @skb: GSO skb
+ * @len: length to validate against
+ *
+ * skb_gso_validate_len validates if a given skb will fit a wanted
+ * length once split, including L2, L3 and L4 headers.
+ *
+ * Similar to skb_gso_validate_mtu, but inclusive of L2 headers.
+ */
+bool skb_gso_validate_len(const struct sk_buff *skb, unsigned int len)
+{
+ const struct skb_shared_info *shinfo = skb_shinfo(skb);
+ const struct sk_buff *iter;
+ unsigned int hlen;
+
+ hlen = skb_gso_mac_seglen(skb);
+
+ if (shinfo->gso_size != GSO_BY_FRAGS)
+ return hlen <= len;
+
+ /* Undo this so we can re-use header sizes */
+ hlen -= GSO_BY_FRAGS;
+
+ skb_walk_frags(skb, iter) {
+ if (hlen + skb_headlen(iter) > len)
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(skb_gso_validate_len);
+
static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
{
if (skb_cow(skb, skb_headroom(skb)) < 0) {
--
2.14.1
