counter overflow provision

diff --git a/pcap_xrate.c b/pcap_xrate.c
index 29a1c691ec91ccce7c9b1f31bb417423b3937f4a..5e0043beaaf48d01815779309e153af45a341288 100644 (file)
--- a/pcap_xrate.c
+++ b/pcap_xrate.c
@@ -9,6 +9,7 @@
  * kontaxis 2015-04-14
  */
 
+#include <limits.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -127,6 +128,31 @@ struct udphdr
 #define unlikely(x)     __builtin_expect((x),0)
 
 
+#define RESET_COUNTERS \
+{\
+       total_pkt_bytes = 0; \
+       total_ip4_bytes = 0; \
+\
+       ts_sec_begin   = 0; \
+       ts_sec_end     = 0; \
+\
+       total_pkts_ok  = 0; \
+       total_pkts_err = 0; \
+}
+
+#define PRINT_COUNTERS \
+{\
+       fprintf(stdout, \
+               "Processed %lu good packets, %lu erroenous" \
+               " between epoch %lu and %lu.\n", \
+               total_pkts_ok, total_pkts_err, ts_sec_begin, ts_sec_end); \
+\
+       fprintf(stdout, \
+               "Counted %lu IPv4 packet bytes or %lu off-the-wire" \
+               " transmitted in %lu seconds.\n", \
+               total_ip4_bytes, total_pkt_bytes, ts_sec_end - ts_sec_begin + 1); \
+}
+
 int main(int argc, char **argv)
 {
        pcap_t * read_handle = NULL;
@@ -163,14 +189,7 @@ int main(int argc, char **argv)
                return 1;
        }
 
-       total_pkt_bytes = 0;
-       total_ip4_bytes = 0;
-
-       ts_sec_begin   = 0;
-       ts_sec_end     = 0;
-
-       total_pkts_ok  = 0;
-       total_pkts_err = 0;
+       RESET_COUNTERS
 
        while ((packet = pcap_next(read_handle, &header)))
        {
@@ -189,6 +208,10 @@ int main(int argc, char **argv)
                                "%lu #%lu WARNING: ether->ether_type != ETHERTYPE_IP. Ignoring.\n",
                                header.ts.tv_sec, total_pkts_ok + total_pkts_err + 1);
 #endif
+                       if (unlikely(ULONG_MAX - total_pkts_err < 1)) {
+                               PRINT_COUNTERS
+                               RESET_COUNTERS
+                       }
                        total_pkts_err++;
                        continue;
                }
@@ -202,26 +225,33 @@ int main(int argc, char **argv)
                        fprintf(stderr, "%lu #%lu WARNING: IP_V(ip) != 4. Ignoring.\n",
                                header.ts.tv_sec, total_pkts_ok + total_pkts_err + 1);
 #endif
+                       if (unlikely(ULONG_MAX - total_pkts_err < 1)) {
+                               PRINT_COUNTERS
+                               RESET_COUNTERS
+                       }
                        total_pkts_err++;
                        continue;
                }
 
+               /* Counter(s) about to overflow. Print what we have so far and reset. */
+               if (unlikely(
+                               ULONG_MAX - total_ip4_bytes < n16toh16(ip->tot_len) ||
+                               ULONG_MAX - total_pkt_bytes < header.len            ||
+                               ULONG_MAX - total_pkts_ok   < 1
+                               )) {
+                       PRINT_COUNTERS
+                       RESET_COUNTERS
+               }
+
                total_ip4_bytes += n16toh16(ip->tot_len);
                total_pkt_bytes += header.len;
 
                total_pkts_ok++;
-  }
+       }
 
        pcap_close(read_handle);
 
-       fprintf(stdout,
-               "Processed %lu good packets, %lu erroenous between epoch %lu and %lu.\n",
-               total_pkts_ok, total_pkts_err, ts_sec_begin, ts_sec_end);
-
-       fprintf(stdout,
-               "Counted %lu IPv4 packet bytes or %lu off-the-wire"
-               " transmitted in %lu seconds.\n",
-               total_ip4_bytes, total_pkt_bytes, ts_sec_end - ts_sec_begin + 1);
+       PRINT_COUNTERS
 
        return 0;
 }