ifpps: fix matching wrong interface/device

There were a bug in ifpps, that would match the first occurance
of a device/interface name in /proc/net/dev, because it located
the device based on a substring.

If the device name were starting with the same characters,
e.g. having a device named eth4 and a VLAN device named eth4.100.
If specifying --dev eth4, then depending on the order of
/proc/net/dev the wrong device could be choosen for stats. (Note
kernel does not guarantee the order of devices in proc file)

Fix the bug, by matching with a colon ':' appended to the device
name, as the kernel proc format prints a ':' behind the device name.

Fixes #119

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/ifpps.c b/ifpps.c
index 6f50bed..785a882 100644
--- a/ifpps.c
+++ b/ifpps.c
@@ -226,12 +226,17 @@ static int stats_proc_net_dev(const char *ifname, struct ifstat *stats)
 {
 	int ret = -EINVAL;
 	char buff[256];
+	char *ifname_colon;
 	FILE *fp;
 
 	fp = fopen("/proc/net/dev", "r");
 	if (!fp)
 		panic("Cannot open /proc/net/dev!\n");
 
+	ifname_colon = xstrndup(ifname, strlen(ifname)+2);
+	ifname_colon[strlen(ifname)]   = ':';
+	ifname_colon[strlen(ifname)+1] = '\0';
+
 	if (fgets(buff, sizeof(buff), fp)) { ; }
 	if (fgets(buff, sizeof(buff), fp)) { ; }
 
@@ -240,7 +245,7 @@ static int stats_proc_net_dev(const char *ifname, struct ifstat *stats)
 	while (fgets(buff, sizeof(buff), fp) != NULL) {
 		buff[sizeof(buff) -1] = 0;
 
-		if (strstr(buff, ifname) == NULL)
+		if (strstr(buff, ifname_colon) == NULL)
 			continue;
 
 		if (sscanf(buff, "%*[a-z0-9 .-]:%llu%llu%llu%llu%llu%llu"
@@ -259,6 +264,7 @@ static int stats_proc_net_dev(const char *ifname, struct ifstat *stats)
 		memset(buff, 0, sizeof(buff));
 	}
 
+	xfree(ifname_colon);
 	fclose(fp);
 	return ret;
 }