Add support for sending packets; includes contributions from Mark

[libpcap] / pcap-bpf.c

diff --git a/pcap-bpf.c b/pcap-bpf.c
index 8585db190c8a395e85853bc951b23320b56cd417..5da81b141df9eee821feab655010e9d174c5a9b3 100644 (file)
--- a/pcap-bpf.c
+++ b/pcap-bpf.c
@@ -20,7 +20,7 @@
  */
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.73 2003-12-24 08:26:24 itojun Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-bpf.c,v 1.74 2004-03-23 19:18:04 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -292,6 +292,29 @@ pcap_read_bpf(pcap_t *p, int cnt, pcap_handler callback, u_char *user)
        return (n);
 }
 
+static int
+pcap_inject_bpf(pcap_t *p, const void *buf, size_t size)
+{
+       int ret;
+
+       /*
+        * Do a BIOCSHDRCMPLT, if defined, to turn that flag on, so
+        * the link-layer source address isn't forcibly overwritten?
+        * (Ignore errors?  Return errors if not "sorry, that ioctl
+        * isn't supported?)
+        *
+        * XXX - I seem to remember some packet-sending bug in some
+        * BSDs - check CVS log for "bpf.c"?
+        */
+       ret = write(p->fd, buf, size);
+       if (ret == -1) {
+               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
+                   pcap_strerror(errno));
+               return (-1);
+       }
+       return (ret);
+}
+
 #ifdef _AIX
 static int 
 bpf_odminit(char *errbuf)
@@ -467,7 +490,23 @@ bpf_open(pcap_t *p, char *errbuf)
         */
        do {
                (void)snprintf(device, sizeof(device), "/dev/bpf%d", n++);
-               fd = open(device, O_RDONLY);
+               /*
+                * Initially try a read/write open (to allow the inject
+                * method to work).  If that fails due to permission
+                * issues, fall back to read-only.  This allows a
+                * non-root user to be granted specific access to pcap
+                * capabilities via file permissions.
+                *
+                * XXX - we should have an API that has a flag that
+                * controls whether to open read-only or read-write,
+                * so that denial of permission to send (or inability
+                * to send, if sending packets isn't supported on
+                * the device in question) can be indicated at open
+                * time.
+                */
+               fd = open(device, O_RDWR);
+               if (fd == -1 && errno == EACCES)
+                       fd = open(device, O_RDONLY);
        } while (fd < 0 && errno == EBUSY);
 
        /*
@@ -898,6 +937,7 @@ pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
        }
 
        p->read_op = pcap_read_bpf;
+       p->inject_op = pcap_inject_bpf;
        p->setfilter_op = pcap_setfilter_bpf;
        p->set_datalink_op = pcap_set_datalink_bpf;
        p->getnonblock_op = pcap_getnonblock_fd;