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Handle the padding stuck in between the 802.11 header and the 802.11 

payload by Atheros cards; check the radiotap header to see whether that
padding is there.
This commit is contained in:
guy 2007-11-08 01:50:52 +00:00
parent f21f24e2b9
commit 5d6374a424
1 changed files with 101 additions and 2 deletions
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103
gencode.c
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@ -21,7 +21,7 @@
*/
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.290.2.9 2007-11-07 19:33:00 guy Exp $ (LBL)";
"@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.290.2.10 2007-11-08 01:50:52 guy Exp $ (LBL)";
#endif
#ifdef HAVE_CONFIG_H
@ -2275,6 +2275,10 @@ gen_load_802_11_header_len(struct slist *s, struct slist *snext)
struct slist *sjset_data_frame_1;
struct slist *sjset_data_frame_2;
struct slist *sjset_qos;
struct slist *sjset_radiotap_flags;
struct slist *sjset_radiotap_tsft;
struct slist *sjset_tsft_datapad, *sjset_notsft_datapad;
struct slist *s_roundup;
if (reg_off_macpl == -1) {
/*
@ -2378,7 +2382,102 @@ gen_load_802_11_header_len(struct slist *s, struct slist *snext)
s2 = new_stmt(BPF_ST);
s2->s.k = reg_off_macpl;
sappend(s, s2);
sjset_qos->s.jf = snext;
/*
* If we have a radiotap header, look at it to see whether
* there's Atheros padding between the MAC-layer header
* and the payload.
*
* Note: all of the fields in the radiotap header are
* little-endian, so we byte-swap all of the values
* we test against, as they will be loaded as big-endian
* values.
*/
if (linktype == DLT_IEEE802_11_RADIO) {
/*
* Is the IEEE80211_RADIOTAP_FLAGS bit (0x0000002) set
* in the presence flag?
*/
sjset_qos->s.jf = s2 = new_stmt(BPF_LD|BPF_ABS|BPF_W);
s2->s.k = 4;
sappend(s, s2);
sjset_radiotap_flags = new_stmt(JMP(BPF_JSET));
sjset_radiotap_flags->s.k = SWAPLONG(0x00000002);
sappend(s, sjset_radiotap_flags);
/*
* If not, skip all of this.
*/
sjset_radiotap_flags->s.jf = snext;
/*
* Otherwise, is the IEEE80211_RADIOTAP_TSFT bit set?
*/
sjset_radiotap_tsft = sjset_radiotap_flags->s.jt =
new_stmt(JMP(BPF_JSET));
sjset_radiotap_tsft->s.k = SWAPLONG(0x00000001);
sappend(s, sjset_radiotap_tsft);
/*
* If IEEE80211_RADIOTAP_TSFT is set, the flags field is
* at an offset of 16 from the beginning of the raw packet
* data (8 bytes for the radiotap header and 8 bytes for
* the TSFT field).
*
* Test whether the IEEE80211_RADIOTAP_F_DATAPAD bit (0x20)
* is set.
*/
sjset_radiotap_tsft->s.jt = s2 = new_stmt(BPF_LD|BPF_ABS|BPF_B);
s2->s.k = 16;
sappend(s, s2);
sjset_tsft_datapad = new_stmt(JMP(BPF_JSET));
sjset_tsft_datapad->s.k = 0x20;
sappend(s, sjset_tsft_datapad);
/*
* If IEEE80211_RADIOTAP_TSFT is not set, the flags field is
* at an offset of 8 from the beginning of the raw packet
* data (8 bytes for the radiotap header).
*
* Test whether the IEEE80211_RADIOTAP_F_DATAPAD bit (0x20)
* is set.
*/
sjset_radiotap_tsft->s.jf = s2 = new_stmt(BPF_LD|BPF_ABS|BPF_B);
s2->s.k = 8;
sappend(s, s2);
sjset_notsft_datapad = new_stmt(JMP(BPF_JSET));
sjset_notsft_datapad->s.k = 0x20;
sappend(s, sjset_notsft_datapad);
/*
* In either case, if IEEE80211_RADIOTAP_F_DATAPAD is
* set, round the length of the 802.11 header to
* a multiple of 4. Do that by adding 3 and then
* dividing by and multiplying by 4, which we do by
* ANDing with ~3.
*/
s_roundup = new_stmt(BPF_LD|BPF_MEM);
s_roundup->s.k = reg_off_macpl;
sappend(s, s_roundup);
s2 = new_stmt(BPF_ALU|BPF_ADD|BPF_IMM);
s2->s.k = 3;
sappend(s, s2);
s2 = new_stmt(BPF_ALU|BPF_AND|BPF_IMM);
s2->s.k = ~3;
sappend(s, s2);
s2 = new_stmt(BPF_ST);
s2->s.k = reg_off_macpl;
sappend(s, s2);
sjset_tsft_datapad->s.jt = s_roundup;
sjset_tsft_datapad->s.jf = snext;
sjset_notsft_datapad->s.jt = s_roundup;
sjset_notsft_datapad->s.jf = snext;
} else
sjset_qos->s.jf = snext;
return s;
}