From 3994535c1d54028ae0a3268e001c9598c7c335ed Mon Sep 17 00:00:00 2001 From: Jeremy Sowden Date: Thu, 16 Mar 2023 11:07:53 +0000 Subject: pcap: simplify opening of output file 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 Signed-off-by: Florian Westphal --- output/pcap/ulogd_output_PCAP.c | 41 ++++++++++++++--------------------------- 1 file changed, 14 insertions(+), 27 deletions(-) (limited to 'output/pcap/ulogd_output_PCAP.c') diff --git a/output/pcap/ulogd_output_PCAP.c b/output/pcap/ulogd_output_PCAP.c index e7798f2..0daa2c9 100644 --- a/output/pcap/ulogd_output_PCAP.c +++ b/output/pcap/ulogd_output_PCAP.c @@ -220,33 +220,20 @@ 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 && + !write_pcap_header(pi)) { + ulogd_log(ULOGD_ERROR, "can't write pcap header: %s\n", + strerror(errno)); + return -ENOSPC; } return 0; -- cgit v1.2.3