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Commit 312fc2b4 authored by John Fastabend's avatar John Fastabend Committed by Daniel Borkmann
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net: do_tcp_sendpages flag to avoid SKBTX_SHARED_FRAG 



When calling do_tcp_sendpages() from in kernel and we know the data
has no references from user side we can omit SKBTX_SHARED_FRAG flag.
This patch adds an internal flag, NO_SKBTX_SHARED_FRAG that can be used
to omit setting SKBTX_SHARED_FRAG.

The flag is not exposed to userspace because the sendpage call from
the splice logic masks out all bits except MSG_MORE.

Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent ffa35660

include/linux/socket.h

+1 −0
Original line number Diff line number Diff line
@@ -287,6 +287,7 @@ struct ucred { 
#define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */

#define MSG_BATCH	0x40000 /* sendmmsg(): more messages coming */

#define MSG_EOF         MSG_FIN

#define MSG_NO_SHARED_FRAGS 0x80000 /* sendpage() internal : page frags are not shared */



#define MSG_ZEROCOPY	0x4000000	/* Use user data in kernel path */

#define MSG_FASTOPEN	0x20000000	/* Send data in TCP SYN */

net/ipv4/tcp.c

+3 −1
Original line number Diff line number Diff line
@@ -994,6 +994,8 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset, 
			get_page(page);

			skb_fill_page_desc(skb, i, page, offset, copy);

		}



		if (!(flags & MSG_NO_SHARED_FRAGS))

			skb_shinfo(skb)->tx_flags |= SKBTX_SHARED_FRAG;



		skb->len += copy;