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Re: [PATCH net-next 4/6] ipvs: fix sparse warnings for sync msg size

To: Simon Horman <horms@xxxxxxxxxxxx>
Subject: Re: [PATCH net-next 4/6] ipvs: fix sparse warnings for sync msg size
Cc: Julian Anastasov <ja@xxxxxx>, lvs-devel@xxxxxxxxxxxxxxx, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
From: Hans Schillstrom <hans@xxxxxxxxxxxxxxx>
Date: Mon, 22 Apr 2013 07:55:51 +0200
Hello Simon

On Mon, 2013-04-22 at 13:05 +0900, Simon Horman wrote:
> On Fri, Apr 19, 2013 at 10:35:04PM +0300, Julian Anastasov wrote:
> > 
> >     Hello,
> > 
> > On Fri, 19 Apr 2013, Simon Horman wrote:
> > 
> > > My idea is as follows:
> > > 
> > > From: Simon Horman <horms@xxxxxxxxxxxx>
> > > 
> > > ipvs: Use network byte order for sync message size
> > > 
> > > struct ip_vs_sync_mesg is both sent across the wire and
> > > used internally to store IPVS synchronisation messages.
> > > 
> > > Up until now the scheme used has been to convert the size field
> > > to network byte order before sending a message on the wire and
> > > convert it to host byte order when sending a message.
> > > 
> > > This patch changes that scheme to always treat the field
> > > as being network byte order. This seems appropriate as
> > > the structure is sent across the wire. And by consistently
> > > treating the field has network byte order it is now possible
> > > to take advantage of sparse to flag any future miss-use.
> > > 
> > > Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>
> > > ---
> > >  net/netfilter/ipvs/ip_vs_sync.c |   15 +++++----------
> > >  1 file changed, 5 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/net/netfilter/ipvs/ip_vs_sync.c 
> > > b/net/netfilter/ipvs/ip_vs_sync.c
> > > index 8e57077..c73778a 100644
> > > --- a/net/netfilter/ipvs/ip_vs_sync.c
> > > +++ b/net/netfilter/ipvs/ip_vs_sync.c
> > > @@ -255,7 +255,7 @@ struct ip_vs_sync_mesg_v0 {
> > >  struct ip_vs_sync_mesg {
> > >   __u8                    reserved;       /* must be zero */
> > >   __u8                    syncid;
> > > - __u16                   size;
> > > + __be16                  size;
> > 
> >     It seems v0 should be changed too,
> > ip_vs_send_sync_msg() handles both versions in sb->mesg.
> 
> Thanks and sorry for missing that.
> How about this?
> 
> From: Simon Horman <horms@xxxxxxxxxxxx>
> 
> ipvs: Use network byte order for sync message size
> 
> struct ip_vs_sync_mesg and ip_vs_sync_mesg_v0 are both sent across the wire
> and used internally to store IPVS synchronisation messages.
> 
> Up until now the scheme used has been to convert the size field
> to network byte order before sending a message on the wire and
> convert it to host byte order when sending a message.
> 
> This patch changes that scheme to always treat the field
> as being network byte order. This seems appropriate as
> the structure is sent across the wire. And by consistently
> treating the field has network byte order it is now possible
> to take advantage of sparse to flag any future miss-use.
> 
> Signed-off-by: Simon Horman <horms@xxxxxxxxxxxx>

It looks good 

Ack-by: Hans Schillstrom <hans@xxxxxxxxxxxxxxx>

> ---
> 
> v2
> * As suggested by Julian Anastasov,
>   update struct ip_vs_sync_mesg_v0  as well as struct ip_vs_sync_mesg.
> ---
>  net/netfilter/ipvs/ip_vs_sync.c | 21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_sync.c b/net/netfilter/ipvs/ip_vs_sync.c
> index 8e57077..f6046d9 100644
> --- a/net/netfilter/ipvs/ip_vs_sync.c
> +++ b/net/netfilter/ipvs/ip_vs_sync.c
> @@ -246,7 +246,7 @@ struct ip_vs_sync_thread_data {
>  struct ip_vs_sync_mesg_v0 {
>       __u8                    nr_conns;
>       __u8                    syncid;
> -     __u16                   size;
> +     __be16                  size;
>  
>       /* ip_vs_sync_conn entries start here */
>  };
> @@ -255,7 +255,7 @@ struct ip_vs_sync_mesg_v0 {
>  struct ip_vs_sync_mesg {
>       __u8                    reserved;       /* must be zero */
>       __u8                    syncid;
> -     __u16                   size;
> +     __be16                  size;
>       __u8                    nr_conns;
>       __s8                    version;        /* SYNC_PROTO_VER  */
>       __u16                   spare;
> @@ -335,7 +335,7 @@ ip_vs_sync_buff_create(struct netns_ipvs *ipvs)
>       sb->mesg->reserved = 0;  /* old nr_conns i.e. must be zero now */
>       sb->mesg->version = SYNC_PROTO_VER;
>       sb->mesg->syncid = ipvs->master_syncid;
> -     sb->mesg->size = sizeof(struct ip_vs_sync_mesg);
> +     sb->mesg->size = htons(sizeof(struct ip_vs_sync_mesg));
>       sb->mesg->nr_conns = 0;
>       sb->mesg->spare = 0;
>       sb->head = (unsigned char *)sb->mesg + sizeof(struct ip_vs_sync_mesg);
> @@ -418,7 +418,7 @@ ip_vs_sync_buff_create_v0(struct netns_ipvs *ipvs)
>       mesg = (struct ip_vs_sync_mesg_v0 *)sb->mesg;
>       mesg->nr_conns = 0;
>       mesg->syncid = ipvs->master_syncid;
> -     mesg->size = sizeof(struct ip_vs_sync_mesg_v0);
> +     mesg->size = htons(sizeof(struct ip_vs_sync_mesg_v0));
>       sb->head = (unsigned char *)mesg + sizeof(struct ip_vs_sync_mesg_v0);
>       sb->end = (unsigned char *)mesg + ipvs->send_mesg_maxlen;
>       sb->firstuse = jiffies;
> @@ -582,7 +582,7 @@ static void ip_vs_sync_conn_v0(struct net *net, struct 
> ip_vs_conn *cp,
>       }
>  
>       m->nr_conns++;
> -     m->size += len;
> +     m->size = htons(ntohs(m->size) + len);
>       buff->head += len;
>  
>       /* check if there is a space for next one */
> @@ -693,7 +693,7 @@ sloop:
>  
>       p = buff->head;
>       buff->head += pad + len;
> -     m->size += pad + len;
> +     m->size = htons(ntohs(m->size) + pad + len);
>       /* Add ev. padding from prev. sync_conn */
>       while (pad--)
>               *(p++) = 0;
> @@ -1175,10 +1175,8 @@ static void ip_vs_process_message(struct net *net, 
> __u8 *buffer,
>               IP_VS_DBG(2, "BACKUP, message header too short\n");
>               return;
>       }
> -     /* Convert size back to host byte order */
> -     m2->size = ntohs(m2->size);
>  
> -     if (buflen != m2->size) {
> +     if (buflen != ntohs(m2->size)) {
>               IP_VS_DBG(2, "BACKUP, bogus message size\n");
>               return;
>       }
> @@ -1544,10 +1542,7 @@ ip_vs_send_sync_msg(struct socket *sock, struct 
> ip_vs_sync_mesg *msg)
>       int msize;
>       int ret;
>  
> -     msize = msg->size;
> -
> -     /* Put size in network byte order */
> -     msg->size = htons(msg->size);
> +     msize = ntohs(msg->size);
>  
>       ret = ip_vs_send_async(sock, (char *)msg, msize);
>       if (ret >= 0 || ret == -EAGAIN)

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