setting rcvbuf

[John Heffner <jheffner () psc edu>]

I've found that on my linux machines, setting the rcvbuf on the packet
socket bigger helps to reduce drops at high rates.

I implemented the following, though I'm not sure how this works on BSD and
other UNIXes.  I'm also only guessing that pcap_setbuff has a similar
meaning under windows and that overloading it makes sense.  Does this seem
like a reasonable thing to do?

Thanks,
  -John


Index: tcpdump.c
===================================================================
RCS file: /tcpdump/master/tcpdump/tcpdump.c,v
retrieving revision 1.243
diff -U3 -r1.243 tcpdump.c
--- tcpdump.c   15 Jun 2004 00:00:04 -0000      1.243
+++ tcpdump.c   15 Jun 2004 21:41:20 -0000
@@ -287,13 +287,8 @@
  * Set up flags that might or might not be supported depending on the
  * version of libpcap we're using.
  */
-#ifdef WIN32
 #define B_FLAG         "B:"
 #define B_FLAG_USAGE   " [ -B size ]"
-#else /* WIN32 */
-#define B_FLAG
-#define B_FLAG_USAGE
-#endif /* WIN32 */

 #ifdef HAVE_PCAP_FINDALLDEVS
 #ifndef HAVE_PCAP_IF_T
@@ -413,8 +408,8 @@
        int devnum;
 #endif
        int status;
-#ifdef WIN32
        u_int UserBufferSize = 1000000;
+#ifdef WIN32
        if(wsockinit() != 0) return 1;
 #endif /* WIN32 */

@@ -459,13 +454,11 @@
                        ++Aflag;
                        break;

-#ifdef WIN32
                case 'B':
                        UserBufferSize = atoi(optarg)*1024;
                        if (UserBufferSize < 0)
                                error("invalid packet buffer size %s", optarg);
                        break;
-#endif /* WIN32 */

                case 'c':
                        cnt = atoi(optarg);
@@ -828,12 +821,10 @@
                if (setgid(getgid()) != 0 || setuid(getuid()) != 0)
                        fprintf(stderr, "Warning: setgid/setuid failed !\n");
 #endif /* WIN32 */
-#ifdef WIN32
                if(UserBufferSize != 1000000)
                        if(pcap_setbuff(pd, UserBufferSize)==-1){
                                error("%s", pcap_geterr(pd));
                        }
-#endif /* WIN32 */
                if (Lflag)
                        show_dlts_and_exit(pd);
                if (gndo->ndo_dlt >= 0) {




Index: pcap-win32.c
===================================================================
RCS file: /tcpdump/master/libpcap/pcap-win32.c,v
retrieving revision 1.22
diff -U3 -r1.22 pcap-win32.c
--- pcap-win32.c        7 Jun 2004 13:27:46 -0000       1.22
+++ pcap-win32.c        15 Jun 2004 21:49:45 -0000
@@ -717,24 +717,6 @@
        return 0;
 }

-/* Set the dimension of the kernel-level capture buffer */
-int
-pcap_setbuff(pcap_t *p, int dim)
-{
-       if (p->adapter==NULL)
-       {
-               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "The kernel buffer size cannot be set while reading from a file");
-               return -1;
-       }
-
-       if(PacketSetBuff(p->adapter,dim)==FALSE)
-       {
-               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "driver error: not enough memory to allocate the kernel buffer");
-               return -1;
-       }
-       return 0;
-}
-
 /*set the minimum amount of data that will release a read call*/
 int
 pcap_setmintocopy(pcap_t *p, int size)
Index: pcap.c
===================================================================
RCS file: /tcpdump/master/libpcap/pcap.c,v
retrieving revision 1.74
diff -U3 -r1.74 pcap.c
--- pcap.c      24 Mar 2004 19:50:54 -0000      1.74
+++ pcap.c      15 Jun 2004 21:49:45 -0000
@@ -44,6 +44,7 @@
 #include <pcap-stdinc.h>
 #else /* WIN32 */
 #include <sys/types.h>
+#include <sys/socket.h>
 #endif /* WIN32 */

 #include <stdio.h>
@@ -520,6 +521,28 @@
 #endif
 }

+/* Set the dimension of the kernel-level capture buffer */
+int
+pcap_setbuff(pcap_t *p, int dim)
+{
+#ifndef WIN32
+       return setsockopt(p->fd, SOL_SOCKET, SO_RCVBUF, &dim, sizeof (dim));
+#else
+       if (p->adapter==NULL)
+       {
+               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "The kernel buffer size cannot be set while reading from a file");
+               return -1;
+       }
+
+       if(PacketSetBuff(p->adapter,dim)==FALSE)
+       {
+               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "driver error: not enough memory to allocate the kernel buffer");
+               return -1;
+       }
+       return 0;
+#endif
+}
+
 #ifndef WIN32
 int
 pcap_get_selectable_fd(pcap_t *p)
Index: pcap.h
===================================================================
RCS file: /tcpdump/master/libpcap/pcap.h,v
retrieving revision 1.50
diff -U3 -r1.50 pcap.h
--- pcap.h      23 Mar 2004 19:18:07 -0000      1.50
+++ pcap.h      15 Jun 2004 21:49:45 -0000
@@ -207,6 +207,7 @@
 /* XXX */
 FILE   *pcap_file(pcap_t *);
 int    pcap_fileno(pcap_t *);
+int     pcap_setbuff(pcap_t *p, int dim);

 pcap_dumper_t *pcap_dump_open(pcap_t *, const char *);
 int    pcap_dump_flush(pcap_dumper_t *);
@@ -230,7 +231,6 @@
  * Win32 definitions
  */

-int pcap_setbuff(pcap_t *p, int dim);
 int pcap_setmode(pcap_t *p, int mode);
 int pcap_setmintocopy(pcap_t *p, int size);


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