Remove an unnecessary overflow check.

We'll be running on a platform where int is 31 bits plus a sign bit
and size_t is either 32 bits or 64 bits, and the extra headers we put in
a "packet packet" will be much less than 2^31 bytes in size, so adding
the maximum packet size (an int, as pcap_snapshot() returns an int) to
the size of those extra headers won't overflow a size_t.

diff --git a/rpcapd/daemon.c b/rpcapd/daemon.c
index 9c035c0e96ce4e2f50039a891d53f07c6f81ba53..fe166f816af4519dced6cba180362f3765a3d7ca 100755 (executable)
--- a/rpcapd/daemon.c
+++ b/rpcapd/daemon.c
@@ -2258,20 +2258,16 @@ daemon_thrdatamain(void *ptr)
                sendbuf = NULL; // we can't allocate a buffer, so nothing to free
                goto error;
        }
-       if ((unsigned int)pcap_snapshot(session->fp) > SIZE_MAX - (sizeof(struct rpcap_header) + sizeof(struct rpcap_pkthdr)))
-       {
-               //
-               // The snapshot length is so large that it would overflow
-               // a size_t.  (Unlikely, but not impossible, on ILP32
-               // platforms; impossible on LP64 and LLP64 platforms, as
-               // pcap_snapshot() returns an int).
-               //
-               rpcapd_log(LOGPRIO_ERROR,
-                   "Unable to allocate the buffer for this child thread: snapshot length of %d is too large",
-                       pcap_snapshot(session->fp));
-               sendbuf = NULL; // we can't allocate a buffer, so nothing to free
-               goto error;
-       }
+       //
+       // size_t is unsigned, and the result of pcap_snapshot() is signed;
+       // on no platform that we support is int larger than size_t.
+       // This means that, unless the extra information we prepend to
+       // a maximum-sized packet is impossibly large, the sum of the
+       // snapshot length and the size of that extra information will
+       // fit in a size_t.
+       //
+       // So we don't need to make sure that sendbufsize will overflow.
+       //
        sendbufsize = sizeof(struct rpcap_header) + sizeof(struct rpcap_pkthdr) + pcap_snapshot(session->fp);
        sendbuf = (char *) malloc (sendbufsize);
        if (sendbuf == NULL)