Re: [Qemu-devel] [PATCH 1/5] net/dump: Add support for receive_iov function

[Thomas Huth]

On Fri, 26 Jun 2015 14:38:42 +0800
Jason Wang <address@hidden> wrote:

> 
> 
> On 06/24/2015 11:56 PM, Thomas Huth wrote:
> > Adding a proper receive_iov function to the net dump module. This
> > will make it easier to support the dump feature for the -netdev
> > option in later patches.
> > Also make the receive functions available to the other parts of the
> > source code so we can later use them for dumping from net.c, too.
> >
> > Signed-off-by: Thomas Huth <address@hidden>
> > ---
> >  net/clients.h |  3 +++
> >  net/dump.c    | 48 ++++++++++++++++++++++++++++++++++++++++--------
> >  2 files changed, 43 insertions(+), 8 deletions(-)
> >
> > diff --git a/net/clients.h b/net/clients.h
> > index d47530e..5092f3d 100644
> > --- a/net/clients.h
> > +++ b/net/clients.h
> > @@ -29,6 +29,9 @@
> >  
> >  int net_init_dump(const NetClientOptions *opts, const char *name,
> >                    NetClientState *peer, Error **errp);
> > +ssize_t net_dump_receive(NetClientState *nc, const uint8_t *buf, size_t 
> > size);
> > +ssize_t net_dump_receive_iov(NetClientState *nc, const struct iovec *iov,
> > +                             int cnt);
> >  
> >  #ifdef CONFIG_SLIRP
> >  int net_init_slirp(const NetClientOptions *opts, const char *name,
> > diff --git a/net/dump.c b/net/dump.c
> > index 02c8064..383718a 100644
> > --- a/net/dump.c
> > +++ b/net/dump.c
> > @@ -57,27 +57,49 @@ struct pcap_sf_pkthdr {
> >      uint32_t len;
> >  };
> >  
> > -static ssize_t dump_receive(NetClientState *nc, const uint8_t *buf, size_t 
> > size)
> > +ssize_t net_dump_receive_iov(NetClientState *nc, const struct iovec *iov,
> > +                             int cnt)
> >  {
> >      DumpState *s = DO_UPCAST(DumpState, nc, nc);
> >      struct pcap_sf_pkthdr hdr;
> >      int64_t ts;
> > -    int caplen;
> > +    int caplen, i;
> > +    size_t size = 0;
> > +    struct iovec dumpiov[cnt + 1];
> >  
> >      /* Early return in case of previous error. */
> >      if (s->fd < 0) {
> >          return size;
> >      }
> >  
> > +    dumpiov[0].iov_base = &hdr;
> > +    dumpiov[0].iov_len = sizeof(hdr);
> > +    caplen = s->pcap_caplen;
> > +
> > +    /* Copy iov, limit maximum size to caplen, and count total input size 
> > */
> > +    for (i = 0; i < cnt; i++) {
> > +        dumpiov[i + 1].iov_base = iov[i].iov_base;
> > +        if (size + iov[i].iov_len <= caplen) {
> > +            dumpiov[i + 1].iov_len = iov[i].iov_len;
> > +        } else if (size < caplen) {
> > +            dumpiov[i + 1].iov_len = caplen - size;
> > +        } else {
> > +            dumpiov[i + 1].iov_len = 0;
> > +        }
> > +        size += iov[i].iov_len;
> > +    }
> 
> I believe we could use iov_copy() here.

Looks like that could do the job, too, thanks for the hint! However, I
also need the total size of bytes in the source iov, so I'd then need to
call iov_size() here, too - but I guess it's ok to loop through the iov
twice since dumping is not really time critical.

 Thomas