gso: Support partial splitting at the frag_list pointer

Since commit 8a29111c7 ("net: gro: allow to build full sized skb")
gro may build buffers with a frag_list. This can hurt forwarding
because most NICs can't offload such packets, they need to be
segmented in software. This patch splits buffers with a frag_list
at the frag_list pointer into buffers that can be TSO offloaded.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 6 deletions

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 5c5964962d0c..bc68da38ea86 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -90,12 +90,6 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
                 goto out;
         }
 
-        /* GSO partial only requires splitting the frame into an MSS
-         * multiple and possibly a remainder.  So update the mss now.
-         */
-        if (features & NETIF_F_GSO_PARTIAL)
-                mss = skb->len - (skb->len % mss);
-
         copy_destructor = gso_skb->destructor == tcp_wfree;
         ooo_okay = gso_skb->ooo_okay;
         /* All segments but the first should have ooo_okay cleared */
@@ -108,6 +102,13 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
         /* Only first segment might have ooo_okay set */
         segs->ooo_okay = ooo_okay;
 
+        /* GSO partial and frag_list segmentation only requires splitting
+         * the frame into an MSS multiple and possibly a remainder, both
+         * cases return a GSO skb. So update the mss now.
+         */
+        if (skb_is_gso(segs))
+                mss *= skb_shinfo(segs)->gso_segs;
+
         delta = htonl(oldlen + (thlen + mss));
 
         skb = segs;