sbm

commit 9ef3c9a6b531f8ce2540b7efa26248038410ac0f
parent fab651ea9c4029a12ec6d84040c19d28ee7833d7
Author: sin <sin@2f30.org>
Date:   Mon, 26 Sep 2016 11:46:54 +0100

Use sysfs for statistics gathering on Linux

The link API exposes 32-bit counters.  This was a problem
for long running sessions.

There is a 64-bit version of the link API but sysfs is probably
the better way to go on Linux systems.

Diffstat:
M
sbm.c
 | 
59
++++++++++++++++++++++++++++++++++++-----------------------

1 file changed, 36 insertions(+), 23 deletions(-)
diff --git a/sbm.c b/sbm.c
@@ -5,7 +5,6 @@
 
 #include <net/if.h>
 #ifdef __linux__
-#include <linux/if_link.h>
 #else
 #include <sys/sysctl.h>
 #include <net/if_dl.h>
@@ -78,32 +77,46 @@ scan(void)
 }
 
 #ifdef __linux__
+int
+readcounter(char *filename, uint64_t *v)
+{
+	char path[PATH_MAX];
+	char buf[BUFSIZ];
+	char *endptr;
+	FILE *fp;
+
+	snprintf(path, sizeof(path),
+	         "/sys/class/net/%s/statistics/%s",
+	         ifname, filename);
+	fp = fopen(path, "r");
+	if (fp == NULL) {
+		*v = 0;
+		return -1;
+	}
+	if (fgets(buf, sizeof(buf), fp) == NULL) {
+		fclose(fp);
+		*v = 0;
+		return -1;
+	}
+	fclose(fp);
+	buf[strcspn(buf, "\n")] = '\0';
+	errno = 0;
+	*v = strtoull(buf, &endptr, 10);
+	if (*endptr != '\0' || errno != 0) {
+		*v = 0;
+		return -1;
+	}
+	return 0;
+}
+
 void
 sample(uint64_t *rxbytes, uint64_t *txbytes,
        uint64_t *rxpps, uint64_t *txpps)
 {
-	struct ifaddrs *ifas, *ifa;
-	struct rtnl_link_stats *stats = NULL;
-
-	if (getifaddrs(&ifas) < 0)
-		err(1, "getifaddrs");
-	for (ifa = ifas; ifa; ifa = ifa->ifa_next) {
-		if (strcmp(ifa->ifa_name, ifname))
-			continue;
-		if (!ifa->ifa_data || !ifa->ifa_addr)
-			break;
-		if (ifa->ifa_addr->sa_family == AF_PACKET) {
-			stats = ifa->ifa_data;
-			*rxbytes = stats->rx_bytes;
-			*txbytes = stats->tx_bytes;
-			*rxpps = stats->rx_packets;
-			*txpps = stats->tx_packets;
-			break;
-		}
-	}
-	freeifaddrs(ifas);
-	if (!stats)
-		errx(1, "interface %s cannot be sampled", ifname);
+	readcounter("rx_bytes", rxbytes);
+	readcounter("tx_bytes", txbytes);
+	readcounter("rx_packets", rxpps);
+	readcounter("tx_packets", txpps);
 }
 #else
 void