Add support for sending packets; includes contributions from Mark

[libpcap] / pcap-pf.c

diff --git a/pcap-pf.c b/pcap-pf.c
index 3fa1c842faee2eba09e6991dc78533a235dbb084..3a59083f4d3829ad105921191ef8e3a0ff02c7e4 100644 (file)
--- a/pcap-pf.c
+++ b/pcap-pf.c
@@ -24,7 +24,7 @@
 
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.86 2004-02-09 06:24:42 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/pcap-pf.c,v 1.87 2004-03-23 19:18:06 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -219,6 +219,20 @@ pcap_read_pf(pcap_t *pc, int cnt, pcap_handler callback, u_char *user)
        return (n);
 }
 
+static int
+pcap_inject_pf(pcap_t *p, const void *buf, size_t size)
+{
+       int ret;
+
+       ret = write(p->fd, buf, size);
+       if (ret == -1) {
+               snprintf(p->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
+                   pcap_strerror(errno));
+               return (-1);
+       }
+       return (ret);
+}                           
+
 static int
 pcap_stats_pf(pcap_t *p, struct pcap_stat *ps)
 {
@@ -299,14 +313,28 @@ pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
                return (0);
        }
        memset(p, 0, sizeof(*p));
-
        /*
+        * 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.
+        *
         * XXX - we assume here that "pfopen()" does not, in fact, modify
         * its argument, even though it takes a "char *" rather than a
         * "const char *" as its first argument.  That appears to be
         * the case, at least on Digital UNIX 4.0.
         */
-       p->fd = pfopen(device, O_RDONLY);
+       p->fd = pfopen(device, O_RDWR);
+       if (p->fd == -1 && errno == EACCES)
+               p->fd = pfopen(device, O_RDONLY);
        if (p->fd < 0) {
                snprintf(ebuf, PCAP_ERRBUF_SIZE, "pf open: %s: %s\n\
 your system may not be properly configured; see the packetfilter(4) man page\n",
@@ -467,6 +495,7 @@ your system may not be properly configured; see the packetfilter(4) man page\n",
        p->selectable_fd = p->fd;
 
        p->read_op = pcap_read_pf;
+       p->inject_op = pcap_inject_pf;
        p->setfilter_op = pcap_setfilter_pf;
        p->set_datalink_op = NULL;      /* can't change data link type */
        p->getnonblock_op = pcap_getnonblock_fd;