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[Openvpn-devel,RFC,net-next,v2,2/9] ovpn: accept frag-list GSO input

Message ID 5baa1d94e29e7b109ffd412b4f1d5d113a319389.1789540779.git.ralf@mandelbit.com
State Superseded
Headers
Series ovpn: preserve GSO and GRO batching |

Commit Message

Ralf Lici Sept. 16, 2026, 6:52 a.m. UTC 
  Forwarded TCP traffic can be coalesced into SKB_GSO_FRAGLIST when the
receiving host has no local TCP socket for the flow. Although ovpn
segments every GSO input itself, it does not advertise NETIF_F_FRAGLIST,
so generic transmit validation segments these aggregates before calling
ovpn_net_xmit. That segmentation is functionally correct, but causes
ovpn_net_xmit to be invoked separately for every resulting packet.

Advertise frag-list storage so ovpn receives the aggregate intact and
performs protocol validation and destination-to-peer lookup once before
segmenting it. Frag-list GSO segmentation recovers the complete child
skbs, which can then be encrypted in place and transmitted
independently. Rebuilding those children into a replacement UDP GSO
aggregate was found to add cost rather than improve throughput.

The feature also admits non-GSO frag lists, which describe one packet
split across several skbs. Let skb_cow_data preserve small lists
directly. If a list exceeds the AEAD scatterlist limit, linearize it and
continue rather than rejecting an otherwise valid packet.

Signed-off-by: Ralf Lici <ralf@mandelbit.com>
---
No changes since v1 https://lore.kernel.org/openvpn-devel/5baa1d94e29e7b109ffd412b4f1d5d113a319389.1789485693.git.ralf@mandelbit.com/

 drivers/net/ovpn/crypto_aead.c | 8 ++++++--
 drivers/net/ovpn/main.c        | 3 ++-
 2 files changed, 8 insertions(+), 3 deletions(-)
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Patch

diff --git a/drivers/net/ovpn/crypto_aead.c b/drivers/net/ovpn/crypto_aead.c
index 74eaf6fac2f5..2af493fd5735 100644
--- a/drivers/net/ovpn/crypto_aead.c
+++ b/drivers/net/ovpn/crypto_aead.c
@@ -168,8 +168,12 @@  int ovpn_aead_encrypt(struct ovpn_peer *peer, struct ovpn_crypto_key_slot *ks,
 	if (unlikely(nfrags < 0))
 		return nfrags;
 
-	if (unlikely(nfrags + 2 > (MAX_SKB_FRAGS + 2)))
-		return -ENOSPC;
+	if (unlikely(nfrags > MAX_SKB_FRAGS)) {
+		ret = skb_linearize(skb);
+		if (unlikely(ret))
+			return ret;
+		nfrags = 1;
+	}
 
 	/* allocate temporary memory for iv, sg and req */
 	tmp = kmalloc(ovpn_aead_crypto_tmp_size(ks->encrypt, nfrags),
diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 28e1eb06e127..ac4e0d85e215 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -158,7 +158,8 @@  static const struct ethtool_ops ovpn_ethtool_ops = {
 static void ovpn_setup(struct net_device *dev)
 {
 	netdev_features_t feat = NETIF_F_HW_CSUM | NETIF_F_SG | NETIF_F_GSO |
-				 NETIF_F_GSO_SOFTWARE | NETIF_F_HIGHDMA;
+				 NETIF_F_GSO_SOFTWARE | NETIF_F_FRAGLIST |
+				 NETIF_F_HIGHDMA;
 
 	dev->needs_free_netdev = true;