netdev - Re: [PATCH] sendfile() and UDP socket

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Date:	Tue, 16 Sep 2008 14:24:43 +1000
From:	Simon Horman <horms@...ge.net.au>
To:	Johann Baudy <johaahn@...il.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: [PATCH] sendfile() and UDP socket

On Tue, Sep 16, 2008 at 02:17:05PM +1000, Simon Horman wrote:
> On Sun, Sep 14, 2008 at 12:25:56PM +0200, Johann Baudy wrote:
> > Hi All,
> > 
> > Sendfile() over UDP socket are currently limited to ~ 64KBytes file (max cork.length).
> > Indeed, if you run sendfile() with a file size > 64KBytes over UDP socket, system call will stop and return ~64KBytes without sending anything on the network.
> > This patch is pushing ongoing frames when frames buffer is full, to prevent overflow.
> > 
> > Signed-off-by: Johann Baudy <johann.baudy@...il.com>
> > 
> >  net/ipv4/udp.c |   15 +++++++++++++++
> >  1 files changed, 15 insertions(+), 0 deletions(-)
> > 
> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> > index 8e42fbb..64e0857 100644
> > --- a/net/ipv4/udp.c
> > +++ b/net/ipv4/udp.c
> > @@ -743,7 +743,22 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
> >  		 size_t size, int flags)
> >  {
> >  	struct udp_sock *up = udp_sk(sk);
> > +	struct inet_sock *inet = inet_sk(sk);
> >  	int ret;
> > +	int fragheaderlen;
> > +	struct ip_options *opt = NULL;
> > +
> > +	lock_sock(sk);
> > +	if (inet->cork.flags & IPCORK_OPT)
> > +		opt = inet->cork.opt;
> > +	fragheaderlen = sizeof(struct iphdr) + (opt ? opt->optlen : 0);
> > +
> > +	if (inet->cork.length + size >= 0xFFFF - fragheaderlen) {
> > +		ret = udp_push_pending_frames(sk);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +	release_sock(sk);
> >  
> >  	if (!up->pending) {
> >  		struct msghdr msg = {	.msg_flags = flags|MSG_MORE };
> 
> Hi,
> 
> I wonder if it is slightly nicer to do without the opt variable.
> I _think_ its safe to access inet->cork.opt->optlen based
> on the (inet->cork.flags & IPCORK_OPT) check.
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index 8e42fbb..969f6cd 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -743,7 +743,21 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
>  		 size_t size, int flags)
>  {
>  	struct udp_sock *up = udp_sk(sk);
> +	struct inet_sock *inet = inet_sk(sk);
>  	int ret;
> +	int fragheaderlen;

Also, I wonder if this should be an unsigned int
as both sizeof(struct iphdr) and inet->cork.opt->optlen are unsigned,
though of different width.

> +
> +	fragheaderlen = sizeof(struct iphdr);
> +	lock_sock(sk);
> +	if (inet->cork.flags & IPCORK_OPT)
> +		fragheaderlen += inet->cork.opt->optlen;
> +
> +	if (inet->cork.length + size >= 0xFFFF - fragheaderlen) {
> +		ret = udp_push_pending_frames(sk);
> +		if (ret)
> +			goto out;
> +	}
> +	release_sock(sk);
>  
>  	if (!up->pending) {
>  		struct msghdr msg = {	.msg_flags = flags|MSG_MORE };

-- 
Simon Horman
  VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
  H: www.vergenet.net/~horms/             W: www.valinux.co.jp/en

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