Helo,
While I was playing with libpcap-0.6.2 library, I noticed than when errbuf
function argument is set to NULL (for example in pcap_lookupdev), the
compiled program return
"segmentation fault". I know that errbuf must be set to char string to
avoid it, but it isn't nice when some absent-minded programmer
forget about it and see "segmentation fault" message.
I attach tiny patch to improve the bug.
--
Karol Kisielewski
Warsaw University of Technology
http://home.elka.pw.edu.pl/~kkisiele
--- inet.c.orig Wed Sep 20 17:10:29 2000
+++ inet.c Tue Sep 11 14:00:49 2001
@@ -98,8 +98,9 @@
static char device[IF_NAMESIZE + 1];
if (getifaddrs(&ifap) != 0) {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "getifaddrs: %s", pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "getifaddrs: %s", pcap_strerror(errno));
return NULL;
}
@@ -126,8 +127,9 @@
}
}
if (mp == NULL) {
- (void)strlcpy(errbuf, "no suitable device found",
- PCAP_ERRBUF_SIZE);
+ if(errbuf)
+ (void)strlcpy(errbuf, "no suitable device found",
+ PCAP_ERRBUF_SIZE);
#ifdef HAVE_FREEIFADDRS
freeifaddrs(ifap);
#else
@@ -155,8 +157,9 @@
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0) {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "socket: %s", pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "socket: %s", pcap_strerror(errno));
return (NULL);
}
@@ -166,8 +169,9 @@
buf = malloc (buf_size);
if (buf == NULL) {
close (fd);
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "out of memory");
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "out of memory");
return (NULL);
}
@@ -177,8 +181,9 @@
if (ioctl(fd, SIOCGIFCONF, (char *)&ifc) < 0
&& errno != EINVAL) {
free (buf);
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "SIOCGIFCONF: %s", pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "SIOCGIFCONF: %s", pcap_strerror(errno));
(void)close(fd);
return (NULL);
}
@@ -217,8 +222,9 @@
if (ioctl(fd, SIOCGIFFLAGS, (char *)&ifr) < 0) {
if (errno == ENXIO)
continue;
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "SIOCGIFFLAGS: %.*s: %s",
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "SIOCGIFFLAGS: %.*s: %s",
(int)sizeof(ifr.ifr_name), ifr.ifr_name,
pcap_strerror(errno));
(void)close(fd);
@@ -246,8 +252,9 @@
}
(void)close(fd);
if (mp == NULL) {
- (void)strlcpy(errbuf, "no suitable device found",
- PCAP_ERRBUF_SIZE);
+ if(errbuf)
+ (void)strlcpy(errbuf, "no suitable device found",
+ PCAP_ERRBUF_SIZE);
free(buf);
return (NULL);
}
@@ -280,8 +287,9 @@
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0) {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
- pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE, "socket: %s",
+ pcap_strerror(errno));
return (-1);
}
memset(&ifr, 0, sizeof(ifr));
@@ -292,12 +300,14 @@
(void)strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) < 0) {
if (errno == EADDRNOTAVAIL) {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "%s: no IPv4 address assigned", device);
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "%s: no IPv4 address assigned", device);
} else {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "SIOCGIFADDR: %s: %s",
- device, pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "SIOCGIFADDR: %s: %s",
+ device, pcap_strerror(errno));
}
(void)close(fd);
return (-1);
@@ -305,8 +315,9 @@
sin = (struct sockaddr_in *)&ifr.ifr_addr;
*netp = sin->sin_addr.s_addr;
if (ioctl(fd, SIOCGIFNETMASK, (char *)&ifr) < 0) {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "SIOCGIFNETMASK: %s: %s", device, pcap_strerror(errno));
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "SIOCGIFNETMASK: %s: %s", device, pcap_strerror(errno));
(void)close(fd);
return (-1);
}
@@ -320,8 +331,9 @@
else if (IN_CLASSC(*netp))
*maskp = IN_CLASSC_NET;
else {
- (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "inet class for 0x%x unknown", *netp);
+ if(errbuf)
+ (void)snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "inet class for 0x%x unknown", *netp);
return (-1);
}
}
--- savefile.c.orig Tue Sep 11 14:07:23 2001
+++ savefile.c Tue Sep 11 14:08:42 2001
@@ -324,7 +324,8 @@
p = (pcap_t *)malloc(sizeof(*p));
if (p == NULL) {
- strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
+ if(errbuf)
+ strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
return (NULL);
}
@@ -339,22 +340,25 @@
else {
fp = fopen(fname, "r");
if (fp == NULL) {
- snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname,
- pcap_strerror(errno));
+ if(errbuf)
+ snprintf(errbuf, PCAP_ERRBUF_SIZE, "%s: %s", fname,
+ pcap_strerror(errno));
goto bad;
}
}
if (fread((char *)&hdr, sizeof(hdr), 1, fp) != 1) {
- snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s",
- pcap_strerror(errno));
+ if(errbuf)
+ snprintf(errbuf, PCAP_ERRBUF_SIZE, "fread: %s",
+ pcap_strerror(errno));
goto bad;
}
magic = hdr.magic;
if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
magic = SWAPLONG(magic);
if (magic != TCPDUMP_MAGIC && magic != PATCHED_TCPDUMP_MAGIC) {
- snprintf(errbuf, PCAP_ERRBUF_SIZE,
- "bad dump file format");
+ if(errbuf)
+ snprintf(errbuf, PCAP_ERRBUF_SIZE,
+ "bad dump file format");
goto bad;
}
p->sf.swapped = 1;
@@ -371,7 +375,8 @@
} else
p->sf.hdrsize = sizeof(struct pcap_sf_pkthdr);
if (hdr.version_major < PCAP_VERSION_MAJOR) {
- snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format");
+ if(errbuf)
+ snprintf(errbuf, PCAP_ERRBUF_SIZE, "archaic file format");
goto bad;
}
p->tzoff = hdr.thiszone;
@@ -402,7 +407,8 @@
p->bufsize = BPF_MAXBUFSIZE;
p->sf.base = (u_char *)malloc(p->bufsize + BPF_ALIGNMENT);
if (p->sf.base == NULL) {
- strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
+ if(errbuf)
+ strlcpy(errbuf, "out of swap", PCAP_ERRBUF_SIZE);
goto bad;
}
p->buffer = p->sf.base + BPF_ALIGNMENT - (linklen % BPF_ALIGNMENT);
