[PATCH RFC net-next 2/6] net: build gso segs in multi release time SO_TXTIME

[Willem de Bruijn]

From: Willem de Bruijn <will...@google.com>

When sending multiple segments per interval and the device supports
hardware segmentation, build one GSO segment per interval.

Signed-off-by: Willem de Bruijn <will...@google.com>
---
 net/core/dev.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 5058083375fb..05f538f0f631 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3379,7 +3379,9 @@ EXPORT_SYMBOL(__skb_gso_segment);
 
 struct sk_buff *skb_gso_segment_txtime(struct sk_buff *skb)
 {
+       const netdev_features_t hw_features = NETIF_F_GSO_UDP_L4;
        int mss_per_ival, mss_in_cur_ival;
+       u16 gso_size_orig, gso_segs_orig;
        struct sk_buff *segs, *seg;
        struct skb_shared_info *sh;
        u64 step_ns, tstamp;
@@ -3401,13 +3403,27 @@ struct sk_buff *skb_gso_segment_txtime(struct sk_buff 
*skb)
        if (sh->gso_segs <= mss_per_ival)
                return NULL;
 
+       /* update gso size and segs to build 1 GSO packet per ival */
+       gso_size_orig = sh->gso_size;
+       gso_segs_orig = sh->gso_segs;
+       if (mss_per_ival > 1 && skb->dev->features & hw_features) {
+               sh->gso_size *= mss_per_ival;
+               sh->gso_segs = DIV_ROUND_UP(sh->gso_segs, mss_per_ival);
+               mss_per_ival = 1;
+       }
+
        segs = skb_gso_segment(skb, NETIF_F_SG | NETIF_F_HW_CSUM);
-       if (IS_ERR_OR_NULL(segs))
+       if (IS_ERR_OR_NULL(segs)) {
+               sh->gso_size = gso_size_orig;
+               sh->gso_segs = gso_segs_orig;
                return segs;
+       }
 
        mss_in_cur_ival = 0;
 
        for (seg = segs; seg; seg = seg->next) {
+               unsigned int data_len, data_off;
+
                seg->tstamp = tstamp & ~0xFF;
 
                mss_in_cur_ival++;
@@ -3415,6 +3431,17 @@ struct sk_buff *skb_gso_segment_txtime(struct sk_buff 
*skb)
                        tstamp += step_ns;
                        mss_in_cur_ival = 0;
                }
+
+               data_off = skb_checksum_start_offset(skb) +
+                          skb->csum_offset + sizeof(__sum16);
+               data_len = seg->len - data_off;
+
+               if (data_len > gso_size_orig) {
+                       sh = skb_shinfo(seg);
+                       sh->gso_type = skb_shinfo(skb)->gso_type;
+                       sh->gso_size = gso_size_orig;
+                       sh->gso_segs = DIV_ROUND_UP(data_len, gso_size_orig);
+               }
        }
 
        return segs;
-- 
2.27.0.278.ge193c7cf3a9-goog