Make prepare_tpacket_socket() a bit more of a straightforward gauntlet.
Try TPACKET_V3 first, if it's defined and if immediate mode was not
requested; return if that succeeds or if it fails for a reason other
than "the kernel doesn't support TPACKET_V3". Then try TPACKET_V2, if
it's defined; return if that succeeds or fails for a reson other than
"the kernel doesn't support TPACKET_V2". Then go with TPACKET_V1 or
TPACKET_V1_64.
Don't set handlep->tp_version to TPACKET_V1 and handlep->tp_hdrlen to
sizeof(struct tpacket_hdr) until after we've found out that the kernel
supports neither TPACKET_V2 nor TPACKET_V3; init_tpacket() sets them if
it succeeds.
diff --git a/pcap-linux.c b/pcap-linux.c
index f251649..6da8ba7 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -3539,7 +3539,10 @@
int val = version;
socklen_t len = sizeof(val);
- /* Probe whether kernel supports the specified TPACKET version */
+ /*
+ * Probe whether kernel supports the specified TPACKET version;
+ * this also gets the length of the header for that version.
+ */
if (getsockopt(handle->fd, SOL_PACKET, PACKET_HDRLEN, &val, &len) < 0) {
if (errno == ENOPROTOOPT || errno == EINVAL)
return 1; /* no */
@@ -3595,11 +3598,10 @@
int ret;
#endif
- handlep->tp_version = TPACKET_V1;
- handlep->tp_hdrlen = sizeof(struct tpacket_hdr);
-
#ifdef HAVE_TPACKET3
/*
+ * Try setting the version to TPACKET_V3.
+ *
* The only mode in which buffering is done on PF_PACKET
* sockets, so that packets might not be delivered
* immediately, is TPACKET_V3 mode.
@@ -3608,37 +3610,59 @@
* if the user has requested immediate mode, we don't
* use TPACKET_V3.
*/
- if (handle->opt.immediate)
- ret = 1; /* pretend TPACKET_V3 couldn't be set */
- else
+ if (!handle->opt.immediate) {
ret = init_tpacket(handle, TPACKET_V3, "TPACKET_V3");
- if (-1 == ret) {
- /* Error during setting up TPACKET_V3. */
- return -1;
- } else if (1 == ret) {
- /* TPACKET_V3 not supported - fall back to TPACKET_V2. */
-#endif /* HAVE_TPACKET3 */
-
-#ifdef HAVE_TPACKET2
- ret = init_tpacket(handle, TPACKET_V2, "TPACKET_V2");
- if (-1 == ret) {
- /* Error during setting up TPACKET_V2. */
+ if (ret == 0) {
+ /*
+ * Success.
+ */
+ return 1;
+ }
+ if (ret == -1) {
+ /*
+ * We failed for some reason other than "the
+ * kernel doesn't support TPACKET_V3".
+ */
return -1;
}
-#endif /* HAVE_TPACKET2 */
-
-#ifdef HAVE_TPACKET3
}
#endif /* HAVE_TPACKET3 */
+#ifdef HAVE_TPACKET2
/*
- * 32-bit userspace + 64-bit kernel + tpacket_v1 are not compatible with
+ * Try setting the version to TPACKET_V2.
+ */
+ ret = init_tpacket(handle, TPACKET_V2, "TPACKET_V2");
+ if (ret == 0) {
+ /*
+ * Success.
+ */
+ return 1;
+ }
+ if (ret == -1) {
+ /*
+ * We failed for some reason other than "the
+ * kernel doesn't support TPACKET_V2".
+ */
+ return -1;
+ }
+#endif /* HAVE_TPACKET2 */
+
+ /*
+ * OK, we're using TPACKET_V1, as that's all the kernel supports.
+ */
+ handlep->tp_version = TPACKET_V1;
+ handlep->tp_hdrlen = sizeof(struct tpacket_hdr);
+
+ /*
+ * 32-bit userspace + 64-bit kernel + TPACKET_V1 are not compatible with
* each other due to platform-dependent data type size differences.
*
- * TPACKET_V1_64 allows using a 64-bit tpacket_v1 header from 32-bit
- * userspace.
+ * If we have a 32-bit userland and a 64-bit kernel, use an
+ * internally-defined TPACKET_V1_64, with which we use a 64-bit
+ * version of the data structures.
*/
- if (handlep->tp_version == TPACKET_V1 && sizeof(long) == 4) {
+ if (sizeof(long) == 4) {
struct utsname utsname;
uname(&utsname);
if (!strcmp("x86_64", utsname.machine)) {
