diff options
author | Guy Harris <guy@alum.mit.edu> | 2005-01-03 10:27:20 +0000 |
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committer | Guy Harris <guy@alum.mit.edu> | 2005-01-03 10:27:20 +0000 |
commit | bcedae3c1f3373c8f46016cb3a45e5b35e00ba13 (patch) | |
tree | bff2f44662cc27b0fb7baca42e5b13f7038cdfa7 /wiretap/netxray.c | |
parent | 0e1e5e9febb5de8f32e9a6528e8140fabb877f13 (diff) |
Add some more comments about the FCS issue.
svn path=/trunk/; revision=12939
Diffstat (limited to 'wiretap/netxray.c')
-rw-r--r-- | wiretap/netxray.c | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/wiretap/netxray.c b/wiretap/netxray.c index 93bc759cdd..678a43327a 100644 --- a/wiretap/netxray.c +++ b/wiretap/netxray.c @@ -544,19 +544,21 @@ int netxray_open(wtap *wth, int *err, gchar **err_info) * Perhaps hdr.realtick[0] is 0x00, in which case time * stamp units in the range 1192960 through 1193215 * correspond to captures with an FCS, but that's still - * a bit bizarre. Note that there are captures with - * a network type of 0 (Ethernet) and capture type - * of 0 (NDIS) that do, and that don't, have 0x34 0x12 - * in them, so it's not as if NDIS captures always lack - * FCSes - although the question then is whether any - * NDIS captures with 0x34 0x12 have frames with an FCS; - * if not, then it might be that no NDIS captures have - * FCSes. + * a bit bizarre. + * + * Note that there are captures with a network type of 0 + * (Ethernet) and capture type of 0 (NDIS) that do, and + * that don't, have 0x34 0x12 in them, and at least one + * of the NDIS captures with 0x34 0x12 in it has FCSes, + * so it's not as if no NDIS captures have an FCS. * * There are also captures with a network type of 4 (WAN), * capture type of 6 (HDLC), and subtype of 2 (T1 PRI) that * do, and that don't, have 0x34 0x12, so there are at least - * some captures taken with a pod that might lack an FCS. + * some captures taken with a WAN pod that might lack an FCS. + * (We haven't yet tried dissecting the 4 bytes at the + * end of packets with hdr_2_x.xxx[2] and hdr_2_x.xxx[3] + * equal to 0xff as an FCS.) * * All captures I've seen that have 0x34 and 0x12 *and* * have at least one frame with an FCS have a value of @@ -569,7 +571,9 @@ int netxray_open(wtap *wth, int *err, gchar **err_info) * not as simple as "xxb[4] = 0x01 means the 4 bytes at * the end are FCSes". Also, there's also at least one * 802.11 capture with an xxb[4] value of 0x01 with junk - * rather than an FCS at the end of the frame. + * rather than an FCS at the end of the frame, so xxb[4] + * isn't an obvious flag to determine whether the + * capture has FCSes. * * There don't seem to be any other values in xxb or xxc * that obviously correspond to frames having an FCS. |