diff mbox series

[Openvpn-devel,RFC,net-next,v2,1/9] ovpn: advertise checksum offload for GSO packets

Message ID 1bbfde37488ade61928554db3a119525adf7b608.1789540779.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State Superseded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 
  ovpn already advertises software GSO support and segments GSO skbs in
its transmit path. However, without checksum offload in the device
features, the networking core has to segment GSO packets before they
reach ovpn because TCP GSO packets normally carry CHECKSUM_PARTIAL
state.

Advertise NETIF_F_HW_CSUM so the stack can pass such packets to ovpn.
Complete partial checksums after any GSO segmentation and before
submitting packets for encryption, since the inner packet checksum can
no longer be fixed after the packet has been encrypted.

Also pass the ovpn feature set to skb_gso_segment with GSO capabilities
masked out: this forces software segmentation, but still lets the
segmenter preserve supported non-GSO properties such as non-linear skb
data instead of needlessly linearizing.

Signed-off-by: Ralf Lici <ralf@mandelbit.com>
---
No changes since v1 https://lore.kernel.org/openvpn-devel/1bbfde37488ade61928554db3a119525adf7b608.1789485693.git.ralf@mandelbit.com/

 drivers/net/ovpn/io.c   | 20 ++++++++++++++++++--
 drivers/net/ovpn/main.c |  2 +-
 2 files changed, 19 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
index 9526f8096da6..112067ded401 100644
--- a/drivers/net/ovpn/io.c
+++ b/drivers/net/ovpn/io.c
@@ -358,6 +358,7 @@  netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct ovpn_priv *ovpn = netdev_priv(dev);
 	struct sk_buff *segments, *curr, *next;
 	struct sk_buff_head skb_list;
+	netdev_features_t features;
 	unsigned int tx_bytes = 0;
 	struct ovpn_peer *peer;
 	__be16 proto;
@@ -392,8 +393,13 @@  netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 	skb_dst_drop(skb);
 
 	if (skb_is_gso(skb)) {
-		segments = skb_gso_segment(skb, 0);
-		if (IS_ERR(segments)) {
+		/* force software segmentation, but keep ovpn's non-GSO feature
+		 * bits so the generated segments can preserve non-linear skb
+		 * data where possible
+		 */
+		features = netif_skb_features(skb);
+		segments = skb_gso_segment(skb, features & ~NETIF_F_GSO_MASK);
+		if (IS_ERR_OR_NULL(segments)) {
 			ret = PTR_ERR(segments);
 			net_err_ratelimited("%s: cannot segment payload packet: %d\n",
 					    netdev_name(dev), ret);
@@ -418,6 +424,16 @@  netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 			continue;
 		}
 
+		/* NETIF_F_HW_CSUM requires completing partial checksums */
+		if (unlikely(curr->ip_summed == CHECKSUM_PARTIAL &&
+			     skb_checksum_help(curr) < 0)) {
+			net_err_ratelimited("%s: skb_checksum_help failed for payload packet\n",
+					    netdev_name(dev));
+			ovpn_dev_dstats_tx_dropped(ovpn->dev);
+			kfree_skb(curr);
+			continue;
+		}
+
 		/* only count what we actually send */
 		tx_bytes += curr->len;
 		__skb_queue_tail(&skb_list, curr);
diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c
index 0708249e9607..28e1eb06e127 100644
--- a/drivers/net/ovpn/main.c
+++ b/drivers/net/ovpn/main.c
@@ -157,7 +157,7 @@  static const struct ethtool_ops ovpn_ethtool_ops = {
 
 static void ovpn_setup(struct net_device *dev)
 {
-	netdev_features_t feat = NETIF_F_SG | NETIF_F_GSO |
+	netdev_features_t feat = NETIF_F_HW_CSUM | NETIF_F_SG | NETIF_F_GSO |
 				 NETIF_F_GSO_SOFTWARE | NETIF_F_HIGHDMA;
 
 	dev->needs_free_netdev = true;