Scan the radiotap header once per packet thus reducing
the parser complexity from O(n^2) to O(n)
---
elements/wifi/radiotapdecap.cc | 37 ++++++++++++++++---------------------
1 file changed, 16 insertions(+), 21 deletions(-)
diff --git a/elements/wifi/radiotapdecap.cc b/elements/wifi/radiotapdecap.cc
index e30f84d..ab91788 100644
--- a/elements/wifi/radiotapdecap.cc
+++ b/elements/wifi/radiotapdecap.cc
@@ -50,6 +50,8 @@ static const int
radiotap_elem_to_bytes[NUM_RADIOTAP_ELEMENTS] =
1, /* IEEE80211_RADIOTAP_DATA_RETRIES */
};
+static u_int8_t *offsets[NUM_RADIOTAP_ELEMENTS];
+
static int rt_el_present(struct ieee80211_radiotap_header *th, u_int32_t
element)
{
if (element > NUM_RADIOTAP_ELEMENTS)
@@ -61,6 +63,8 @@ static int rt_check_header(struct ieee80211_radiotap_header
*th, int len)
{
int bytes = 0;
int x = 0;
+ u_int8_t *ptr = (u_int8_t *)(th + 1);
+
if (th->it_version != 0) {
return 0;
}
@@ -70,8 +74,10 @@ static int rt_check_header(struct ieee80211_radiotap_header
*th, int len)
}
for (x = 0; x < NUM_RADIOTAP_ELEMENTS; x++) {
- if (rt_el_present(th, x))
+ if (rt_el_present(th, x)) {
+ offsets[x] = ptr + bytes;
bytes += radiotap_elem_to_bytes[x];
+ }
}
if (le16_to_cpu(th->it_len) < sizeof(struct ieee80211_radiotap_header)
+ bytes) {
@@ -85,17 +91,6 @@ static int rt_check_header(struct ieee80211_radiotap_header
*th, int len)
return 1;
}
-static u_int8_t *rt_el_offset(struct ieee80211_radiotap_header *th, u_int32_t
element) {
- unsigned int x = 0;
- u_int8_t *offset = ((u_int8_t *) th) +
sizeof(ieee80211_radiotap_header);
- for (x = 0; x < NUM_RADIOTAP_ELEMENTS && x < element; x++) {
- if (rt_el_present(th, x))
- offset += radiotap_elem_to_bytes[x];
- }
-
- return offset;
-}
-
RadiotapDecap::RadiotapDecap()
{
}
@@ -121,7 +116,7 @@ RadiotapDecap::simple_action(Packet *p)
ceh->magic = WIFI_EXTRA_MAGIC;
if (rt_el_present(th, IEEE80211_RADIOTAP_FLAGS)) {
- u_int8_t flags = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_FLAGS));
+ u_int8_t flags = *offsets[IEEE80211_RADIOTAP_FLAGS];
if (flags & IEEE80211_RADIOTAP_F_DATAPAD) {
ceh->pad = 1;
}
@@ -131,36 +126,36 @@ RadiotapDecap::simple_action(Packet *p)
}
if (rt_el_present(th, IEEE80211_RADIOTAP_RATE)) {
- ceh->rate = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_RATE));
+ ceh->rate = *offsets[IEEE80211_RADIOTAP_RATE];
}
if (rt_el_present(th, IEEE80211_RADIOTAP_DBM_ANTSIGNAL))
- ceh->rssi = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_DBM_ANTSIGNAL));
+ ceh->rssi = *offsets[IEEE80211_RADIOTAP_DBM_ANTSIGNAL];
if (rt_el_present(th, IEEE80211_RADIOTAP_DBM_ANTNOISE))
- ceh->silence = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_DBM_ANTNOISE));
+ ceh->silence =
*offsets[IEEE80211_RADIOTAP_DBM_ANTNOISE];
if (rt_el_present(th, IEEE80211_RADIOTAP_DB_ANTSIGNAL))
- ceh->rssi = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_DB_ANTSIGNAL));
+ ceh->rssi = *offsets[IEEE80211_RADIOTAP_DB_ANTSIGNAL];
if (rt_el_present(th, IEEE80211_RADIOTAP_DB_ANTNOISE))
- ceh->silence = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_DB_ANTNOISE));
+ ceh->silence = *offsets[IEEE80211_RADIOTAP_DB_ANTNOISE];
if (rt_el_present(th, IEEE80211_RADIOTAP_RX_FLAGS)) {
- u_int16_t flags = le16_to_cpu(*((u_int16_t *)
rt_el_offset(th, IEEE80211_RADIOTAP_RX_FLAGS)));
+ u_int16_t flags = le16_to_cpu(*((u_int16_t *)
offsets[IEEE80211_RADIOTAP_RX_FLAGS]));
if (flags & IEEE80211_RADIOTAP_F_RX_BADFCS)
ceh->flags |= WIFI_EXTRA_RX_ERR;
}
if (rt_el_present(th, IEEE80211_RADIOTAP_TX_FLAGS)) {
- u_int16_t flags = le16_to_cpu(*((u_int16_t *)
rt_el_offset(th, IEEE80211_RADIOTAP_TX_FLAGS)));
+ u_int16_t flags = le16_to_cpu(*((u_int16_t *)
offsets[IEEE80211_RADIOTAP_TX_FLAGS]));
ceh->flags |= WIFI_EXTRA_TX;
if (flags & IEEE80211_RADIOTAP_F_TX_FAIL)
ceh->flags |= WIFI_EXTRA_TX_FAIL;
}
if (rt_el_present(th, IEEE80211_RADIOTAP_DATA_RETRIES))
- ceh->retries = *((u_int8_t *) rt_el_offset(th,
IEEE80211_RADIOTAP_DATA_RETRIES));
+ ceh->retries =
*offsets[IEEE80211_RADIOTAP_DATA_RETRIES];
p->pull(le16_to_cpu(th->it_len));
p->set_mac_header(p->data()); // reset mac-header pointer
--
1.8.3.2
_______________________________________________
click mailing list
[email protected]
https://amsterdam.lcs.mit.edu/mailman/listinfo/click
