Add support for DSA link-layer types

[libpcap] / pcap-linux.c

diff --git a/pcap-linux.c b/pcap-linux.c
index 19bd86592215e18fb1dbd9ec4aae5f8da475fe29..f7c456ffbd4587a40ef939ef0db15cdb180289c1 100644 (file)
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -332,7 +332,6 @@ struct pcap_linux {
 #ifdef HAVE_SYS_EVENTFD_H
        int poll_breakloop_fd; /* fd to an eventfd to break from blocking operations */
 #endif
-
 };
 
 /*
@@ -506,6 +505,9 @@ static struct sock_fprog    total_fcode
        = { 1, &total_insn };
 #endif /* SO_ATTACH_FILTER */
 
+static int     iface_dsa_get_proto_info(const char *device, pcap_t *handle,
+    char *ebuf);
+
 pcap_t *
 pcap_create_interface(const char *device, char *ebuf)
 {
@@ -3298,6 +3300,28 @@ static void map_arphrd_to_dlt(pcap_t *handle, int sock_fd, int arptype,
                 * others?
                 */
                if (!is_wifi(sock_fd, device)) {
+                       int ret;
+
+                       /*
+                        * This is not a Wi-Fi device but it could be
+                        * a DSA master/management network device.
+                        */
+                       ret = iface_dsa_get_proto_info(device, handle,
+                                                      handle->errbuf);
+                       if (ret < 0)
+                               return;
+
+                       if (ret == 1) {
+                               /*
+                                * This is a DSA master/management network
+                                * device linktype is already set by
+                                * iface_dsa_get_proto_info() set an
+                                * appropriate offset here.
+                                */
+                               handle->offset = 2;
+                               break;
+                       }
+
                        /*
                         * It's not a Wi-Fi device; offer DOCSIS.
                         */
@@ -6900,6 +6924,78 @@ iface_get_offload(pcap_t *handle _U_)
 
 #endif /* HAVE_PF_PACKET_SOCKETS */
 
+static struct dsa_proto {
+       const char *name;
+       bpf_u_int32 linktype;
+} dsa_protos[] = {
+       /*
+        * None is special and indicates that the interface does not have
+        * any tagging protocol configured, and is therefore a standard
+        * Ethernet interface.
+        */
+       { "none", DLT_EN10MB },
+       { "brcm", DLT_DSA_TAG_BRCM },
+       { "brcm-prepend", DLT_DSA_TAG_BRCM_PREPEND },
+};
+
+static int     iface_dsa_get_proto_info(const char *device, pcap_t *handle,
+    char *ebuf)
+{
+       char *pathstr;
+       unsigned int i;
+       char buf[256];
+       ssize_t r;
+       int fd;
+
+       fd = asprintf(&pathstr, "/sys/class/net/%s/dsa/tagging", device);
+       if (fd < 0) {
+               pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
+                                         fd, "asprintf");
+               return PCAP_ERROR;
+       }
+
+       fd = open(pathstr, O_RDONLY);
+       free(pathstr);
+       /*
+        * This is not fatal, kernel >= 4.20 *might* expose this attribute
+        */
+       if (fd < 0)
+               return 0;
+
+       r = read(fd, buf, sizeof(buf) - 1);
+       close(fd);
+       if (r <= 0) {
+               pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
+                                         r, "read");
+               return PCAP_ERROR;
+       }
+
+       /*
+        * Buffer should be LF terminated.
+        */
+       if (buf[r - 1] == '\n')
+               r--;
+       buf[r] = '\0';
+
+       for (i = 0; i < sizeof(dsa_protos) / sizeof(dsa_protos[0]); i++) {
+               if (strlen(dsa_protos[i].name) == r &&
+                   !strcmp(buf, dsa_protos[i].name)) {
+                       handle->linktype = dsa_protos[i].linktype;
+                       switch (dsa_protos[i].linktype) {
+                       case DLT_EN10MB:
+                               return 0;
+                       default:
+                               return 1;
+                       }
+               }
+       }
+
+       pcap_snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
+                     "unsupported DSA tag: %s", buf);
+
+       return PCAP_ERROR;
+}
+
 /* ===== Functions to interface to the older kernels ================== */
 
 /*