On 2023-03-16, at 20:02:15 +0100, Pablo Neira Ayuso wrote:
> On Thu, Mar 16, 2023 at 11:07:53AM +0000, Jeremy Sowden wrote:
> > Instead of statting the file, and choosing the mode with which to open
> > it and whether to write the PCAP header based on the result, always open
> > it with mode "a" and _then_ stat it. This simplifies the flow-control
> > and avoids a race between statting and opening.
> >
> > Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx>
> > ---
> > output/pcap/ulogd_output_PCAP.c | 42 ++++++++++++---------------------
> > 1 file changed, 15 insertions(+), 27 deletions(-)
> >
> > diff --git a/output/pcap/ulogd_output_PCAP.c b/output/pcap/ulogd_output_PCAP.c
> > index e7798f20c8fc..220fc6dec5fe 100644
> > --- a/output/pcap/ulogd_output_PCAP.c
> > +++ b/output/pcap/ulogd_output_PCAP.c
> > @@ -220,33 +220,21 @@ static int append_create_outfile(struct ulogd_pluginstance *upi)
> > {
> > struct pcap_instance *pi = (struct pcap_instance *) &upi->private;
> > char *filename = upi->config_kset->ces[0].u.string;
> > - struct stat st_dummy;
> > - int exist = 0;
> > -
> > - if (stat(filename, &st_dummy) == 0 && st_dummy.st_size > 0)
> > - exist = 1;
> > -
> > - if (!exist) {
> > - pi->of = fopen(filename, "w");
> > - if (!pi->of) {
> > - ulogd_log(ULOGD_ERROR, "can't open pcap file %s: %s\n",
> > - filename,
> > - strerror(errno));
> > - return -EPERM;
> > - }
> > - if (!write_pcap_header(pi)) {
> > - ulogd_log(ULOGD_ERROR, "can't write pcap header: %s\n",
> > - strerror(errno));
> > - return -ENOSPC;
> > - }
> > - } else {
> > - pi->of = fopen(filename, "a");
> > - if (!pi->of) {
> > - ulogd_log(ULOGD_ERROR, "can't open pcap file %s: %s\n",
> > - filename,
> > - strerror(errno));
> > - return -EPERM;
> > - }
> > + struct stat st_of;
> > +
> > + pi->of = fopen(filename, "a");
> > + if (!pi->of) {
> > + ulogd_log(ULOGD_ERROR, "can't open pcap file %s: %s\n",
> > + filename,
> > + strerror(errno));
> > + return -EPERM;
> > + }
> > + if (fstat(fileno(pi->of), &st_of) == 0 && st_of.st_size == 0) {
> > + if (!write_pcap_header(pi)) {
> ^^^^
> coding style nitpick,
Whoops. Not sure what happened there.
> it can be fixed before applying it.
Please.
J.
> > + ulogd_log(ULOGD_ERROR, "can't write pcap header: %s\n",
> > + strerror(errno));
> > + return -ENOSPC;
> > + }
> > }
> >
> > return 0;
> > --
> > 2.39.2
> >
>
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