netdev - [PATCH v2 3/7] sk_buff: allow segmenting based on frag sizes

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Message-Id: <e5c12d2bba1cb7f1c199c04d52e481cdd39107e7.1464718103.git.marcelo.leitner@gmail.com>
Date:	Tue, 31 May 2016 15:55:46 -0300
From:	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:	netdev@...r.kernel.org
Cc:	linux-sctp@...r.kernel.org, Xin Long <lucien.xin@...il.com>,
	Neil Horman <nhorman@...driver.com>,
	David Laight <David.Laight@...LAB.COM>,
	Vlad Yasevich <vyasevich@...il.com>,
	Alexander Duyck <alexander.duyck@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Florian Westphal <fw@...len.de>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v2 3/7] sk_buff: allow segmenting based on frag sizes

This patch allows segmenting a skb based on its frags sizes instead of
based on a fixed value.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Tested-by: Xin Long <lucien.xin@...il.com>
---
 include/linux/skbuff.h |  5 +++++
 net/core/skbuff.c      | 10 +++++++---
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c413c588a24f854be9e4df78d8a6872b6b1ff9f3..1f713541cb2fc232cb0e8417232cb9942409c9fc 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -301,6 +301,11 @@ struct sk_buff;
 #endif
 extern int sysctl_max_skb_frags;
 
+/* Set skb_shinfo(skb)->gso_size to this in case you want skb_segment to
+ * segment using its current segmentation instead.
+ */
+#define GSO_BY_FRAGS	0xFFFF
+
 typedef struct skb_frag_struct skb_frag_t;
 
 struct skb_frag_struct {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4724bcf9b0cae1cecbe5bc2c04e308bb70b3232a..97c32c75e704af1f31b064e8f1e0475ff1505d67 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3116,9 +3116,13 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 		int hsize;
 		int size;
 
-		len = head_skb->len - offset;
-		if (len > mss)
-			len = mss;
+		if (unlikely(mss == GSO_BY_FRAGS)) {
+			len = list_skb->len;
+		} else {
+			len = head_skb->len - offset;
+			if (len > mss)
+				len = mss;
+		}
 
 		hsize = skb_headlen(head_skb) - offset;
 		if (hsize < 0)
-- 
2.5.5