Mesh peer links are established only if average rssi of the peer
candidate satisfies the threshold. This is not in 802.11s specification
but was requested by David Fulgham, an open80211s user. This is a way to avoid
marginal peer links with stations that are barely within range.
This patch adds a new mesh configuration parameter, mesh_rssi_threshold. This
feature is supported only for hardwares that report signal in dBm.
Signed-off-by: Ashok Nagarajan <[email protected]>
Signed-off-by: Javier Cardona <[email protected]>
---
v3:
use s32 instead of int32_t (Kalle Valo)
Feature to be supported for devices reporting signal in dBm (Johannes)
v4:
Fix potential null pointer deferencing (Dan Carpenter)
include/linux/nl80211.h | 5 +++++
include/net/cfg80211.h | 1 +
net/mac80211/cfg.c | 8 ++++++++
net/mac80211/debugfs_netdev.c | 2 ++
net/mac80211/mesh_plink.c | 17 ++++++++++++++++-
net/wireless/mesh.c | 3 +++
net/wireless/nl80211.c | 5 +++++
7 files changed, 40 insertions(+), 1 deletions(-)
diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
index be35a68..d6ae590 100644
--- a/include/linux/nl80211.h
+++ b/include/linux/nl80211.h
@@ -2112,6 +2112,10 @@ enum nl80211_mntr_flags {
* @NL80211_MESHCONF_FORWARDING: set Mesh STA as forwarding or non-forwarding
* or forwarding entity (default is TRUE - forwarding entity)
*
+ * @NL80211_MESHCONF_RSSI_THRESHOLD: RSSI threshold in dBm. This specifies the
+ * threshold for average signal strength of candidate station to establish
+ * a peer link.
+ *
* @NL80211_MESHCONF_ATTR_MAX: highest possible mesh configuration attribute
*
* @__NL80211_MESHCONF_ATTR_AFTER_LAST: internal use
@@ -2137,6 +2141,7 @@ enum nl80211_meshconf_params {
NL80211_MESHCONF_GATE_ANNOUNCEMENTS,
NL80211_MESHCONF_HWMP_PERR_MIN_INTERVAL,
NL80211_MESHCONF_FORWARDING,
+ NL80211_MESHCONF_RSSI_THRESHOLD,
/* keep last */
__NL80211_MESHCONF_ATTR_AFTER_LAST,
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 755a770..27e54e3 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -809,6 +809,7 @@ struct mesh_config {
* Still keeping the same nomenclature to be in sync with the spec. */
bool dot11MeshGateAnnouncementProtocol;
bool dot11MeshForwarding;
+ s32 rssi_threshold;
};
/**
diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index f7eb25a..ef9bbb8 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1314,6 +1314,14 @@ static int ieee80211_update_mesh_config(struct wiphy *wiphy,
}
if (_chg_mesh_attr(NL80211_MESHCONF_FORWARDING, mask))
conf->dot11MeshForwarding = nconf->dot11MeshForwarding;
+ if (_chg_mesh_attr(NL80211_MESHCONF_RSSI_THRESHOLD, mask)) {
+ /* our RSSI threshold implementation is supported only for
+ * devices that report signal in dBm.
+ */
+ if (!(sdata->local->hw.flags & IEEE80211_HW_SIGNAL_DBM))
+ return -ENOTSUPP;
+ conf->rssi_threshold = nconf->rssi_threshold;
+ }
return 0;
}
diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 510ed1d..9f484d8 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -443,6 +443,7 @@ IEEE80211_IF_FILE(dot11MeshGateAnnouncementProtocol,
IEEE80211_IF_FILE(dot11MeshHWMPRannInterval,
u.mesh.mshcfg.dot11MeshHWMPRannInterval, DEC);
IEEE80211_IF_FILE(dot11MeshForwarding, u.mesh.mshcfg.dot11MeshForwarding, DEC);
+IEEE80211_IF_FILE(rssi_threshold, u.mesh.mshcfg.rssi_threshold, DEC);
#endif
@@ -581,6 +582,7 @@ static void add_mesh_config(struct ieee80211_sub_if_data *sdata)
MESHPARAMS_ADD(dot11MeshHWMPRootMode);
MESHPARAMS_ADD(dot11MeshHWMPRannInterval);
MESHPARAMS_ADD(dot11MeshGateAnnouncementProtocol);
+ MESHPARAMS_ADD(rssi_threshold);
#undef MESHPARAMS_ADD
}
#endif
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 8806e5e..4e53c4c 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -31,6 +31,12 @@
#define dot11MeshHoldingTimeout(s) (s->u.mesh.mshcfg.dot11MeshHoldingTimeout)
#define dot11MeshMaxPeerLinks(s) (s->u.mesh.mshcfg.dot11MeshMaxPeerLinks)
+/* We only need a valid sta if user configured a minimum rssi_threshold. */
+#define rssi_threshold_check(sta, sdata) \
+ (sdata->u.mesh.mshcfg.rssi_threshold == 0 ||\
+ (sta && (s8) -ewma_read(&sta->avg_signal) > \
+ sdata->u.mesh.mshcfg.rssi_threshold))
+
enum plink_event {
PLINK_UNDEFINED,
OPN_ACPT,
@@ -301,7 +307,8 @@ void mesh_neighbour_update(u8 *hw_addr, u32 rates,
if (mesh_peer_accepts_plinks(elems) &&
sta->plink_state == NL80211_PLINK_LISTEN &&
sdata->u.mesh.accepting_plinks &&
- sdata->u.mesh.mshcfg.auto_open_plinks)
+ sdata->u.mesh.mshcfg.auto_open_plinks &&
+ rssi_threshold_check(sta, sdata))
mesh_plink_open(sta);
rcu_read_unlock();
@@ -531,6 +538,14 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata, struct ieee80211_m
return;
}
+ if (ftype == WLAN_SP_MESH_PEERING_OPEN &&
+ !rssi_threshold_check(sta, sdata)) {
+ mpl_dbg("Mesh plink: %pM does not meet rssi threshold\n",
+ mgmt->sa);
+ rcu_read_unlock();
+ return;
+ }
+
if (sta && !test_sta_flag(sta, WLAN_STA_AUTH)) {
mpl_dbg("Mesh plink: Action frame from non-authed peer\n");
rcu_read_unlock();
diff --git a/net/wireless/mesh.c b/net/wireless/mesh.c
index 9d3e3b6..ba21ab2 100644
--- a/net/wireless/mesh.c
+++ b/net/wireless/mesh.c
@@ -23,6 +23,8 @@
#define MESH_PERR_MIN_INT 100
#define MESH_DIAM_TRAVERSAL_TIME 50
+#define MESH_RSSI_THRESHOLD 0
+
/*
* A path will be refreshed if it is used PATH_REFRESH_TIME milliseconds
* before timing out. This way it will remain ACTIVE and no data frames
@@ -56,6 +58,7 @@ const struct mesh_config default_mesh_config = {
.dot11MeshHWMPRannInterval = MESH_RANN_INTERVAL,
.dot11MeshGateAnnouncementProtocol = false,
.dot11MeshForwarding = true,
+ .rssi_threshold = MESH_RSSI_THRESHOLD,
};
const struct mesh_setup default_mesh_setup = {
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 1998c36..25a470a 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -3290,6 +3290,8 @@ static int nl80211_get_mesh_config(struct sk_buff *skb,
cur_params.dot11MeshGateAnnouncementProtocol);
NLA_PUT_U8(msg, NL80211_MESHCONF_FORWARDING,
cur_params.dot11MeshForwarding);
+ NLA_PUT_U32(msg, NL80211_MESHCONF_RSSI_THRESHOLD,
+ cur_params.rssi_threshold);
nla_nest_end(msg, pinfoattr);
genlmsg_end(msg, hdr);
return genlmsg_reply(msg, info);
@@ -3322,6 +3324,7 @@ static const struct nla_policy nl80211_meshconf_params_policy[NL80211_MESHCONF_A
[NL80211_MESHCONF_HWMP_RANN_INTERVAL] = { .type = NLA_U16 },
[NL80211_MESHCONF_GATE_ANNOUNCEMENTS] = { .type = NLA_U8 },
[NL80211_MESHCONF_FORWARDING] = { .type = NLA_U8 },
+ [NL80211_MESHCONF_RSSI_THRESHOLD] = { .type = NLA_U32},
};
static const struct nla_policy
@@ -3413,6 +3416,8 @@ do {\
nla_get_u8);
FILL_IN_MESH_PARAM_IF_SET(tb, cfg, dot11MeshForwarding,
mask, NL80211_MESHCONF_FORWARDING, nla_get_u8);
+ FILL_IN_MESH_PARAM_IF_SET(tb, cfg, rssi_threshold,
+ mask, NL80211_MESHCONF_RSSI_THRESHOLD, nla_get_u32);
if (mask_out)
*mask_out = mask;
--
1.7.5.4
On Tue, Mar 06, 2012 at 02:33:50PM -0500, John W. Linville wrote:
> On Tue, Mar 06, 2012 at 11:23:30AM -0800, Ashok Nagarajan wrote:
> > Mesh peer links are established only if average rssi of the peer
> > candidate satisfies the threshold. This is not in 802.11s specification
> > but was requested by David Fulgham, an open80211s user. This is a way to avoid
> > marginal peer links with stations that are barely within range.
> >
> > This patch adds a new mesh configuration parameter, mesh_rssi_threshold. This
> > feature is supported only for hardwares that report signal in dBm.
> >
> > Signed-off-by: Ashok Nagarajan <[email protected]>
> > Signed-off-by: Javier Cardona <[email protected]>
> > ---
> > v3:
> > use s32 instead of int32_t (Kalle Valo)
> > Feature to be supported for devices reporting signal in dBm (Johannes)
> >
> > v4:
> > Fix potential null pointer deferencing (Dan Carpenter)
>
> I already merged v3 yesterday -- can you rework this as a fix instead?
Mail server problems, this was delayed. I see that you already sent a new one.
John
--
John W. Linville Someday the world will need a hero, and you
[email protected] might be all we have. Be ready.
Please don't apply this patch. A fix-up patch is coming.
Thanks,
Ashok
On Tue, Mar 6, 2012 at 11:23 AM, Ashok Nagarajan <[email protected]> wrote:
> Mesh peer links are established only if average rssi of the peer
> candidate satisfies the threshold. This is not in 802.11s specification
> but was requested by David Fulgham, an open80211s user. This is a way to avoid
> marginal peer links with stations that are barely within range.
>
> This patch adds a new mesh configuration parameter, mesh_rssi_threshold. This
> feature is supported only for hardwares that report signal in dBm.
>
> Signed-off-by: Ashok Nagarajan <[email protected]>
> Signed-off-by: Javier Cardona <[email protected]>
> ---
> v3:
> use s32 instead of int32_t (Kalle Valo)
> Feature to be supported for devices reporting signal in dBm (Johannes)
>
> v4:
> Fix potential null pointer deferencing (Dan Carpenter)
>
> ?include/linux/nl80211.h ? ? ? | ? ?5 +++++
> ?include/net/cfg80211.h ? ? ? ?| ? ?1 +
> ?net/mac80211/cfg.c ? ? ? ? ? ?| ? ?8 ++++++++
> ?net/mac80211/debugfs_netdev.c | ? ?2 ++
> ?net/mac80211/mesh_plink.c ? ? | ? 17 ++++++++++++++++-
> ?net/wireless/mesh.c ? ? ? ? ? | ? ?3 +++
> ?net/wireless/nl80211.c ? ? ? ?| ? ?5 +++++
> ?7 files changed, 40 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/nl80211.h b/include/linux/nl80211.h
> index be35a68..d6ae590 100644
> --- a/include/linux/nl80211.h
> +++ b/include/linux/nl80211.h
> @@ -2112,6 +2112,10 @@ enum nl80211_mntr_flags {
> ?* @NL80211_MESHCONF_FORWARDING: set Mesh STA as forwarding or non-forwarding
> ?* or forwarding entity (default is TRUE - forwarding entity)
> ?*
> + * @NL80211_MESHCONF_RSSI_THRESHOLD: RSSI threshold in dBm. This specifies the
> + * threshold for average signal strength of candidate station to establish
> + * a peer link.
> + ?*
> ?* @NL80211_MESHCONF_ATTR_MAX: highest possible mesh configuration attribute
> ?*
> ?* @__NL80211_MESHCONF_ATTR_AFTER_LAST: internal use
> @@ -2137,6 +2141,7 @@ enum nl80211_meshconf_params {
> ? ? ? ?NL80211_MESHCONF_GATE_ANNOUNCEMENTS,
> ? ? ? ?NL80211_MESHCONF_HWMP_PERR_MIN_INTERVAL,
> ? ? ? ?NL80211_MESHCONF_FORWARDING,
> + ? ? ? NL80211_MESHCONF_RSSI_THRESHOLD,
>
> ? ? ? ?/* keep last */
> ? ? ? ?__NL80211_MESHCONF_ATTR_AFTER_LAST,
> diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
> index 755a770..27e54e3 100644
> --- a/include/net/cfg80211.h
> +++ b/include/net/cfg80211.h
> @@ -809,6 +809,7 @@ struct mesh_config {
> ? ? ? ? * Still keeping the same nomenclature to be in sync with the spec. */
> ? ? ? ?bool ?dot11MeshGateAnnouncementProtocol;
> ? ? ? ?bool dot11MeshForwarding;
> + ? ? ? s32 ?rssi_threshold;
> ?};
>
> ?/**
> diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
> index f7eb25a..ef9bbb8 100644
> --- a/net/mac80211/cfg.c
> +++ b/net/mac80211/cfg.c
> @@ -1314,6 +1314,14 @@ static int ieee80211_update_mesh_config(struct wiphy *wiphy,
> ? ? ? ?}
> ? ? ? ?if (_chg_mesh_attr(NL80211_MESHCONF_FORWARDING, mask))
> ? ? ? ? ? ? ? ?conf->dot11MeshForwarding = nconf->dot11MeshForwarding;
> + ? ? ? if (_chg_mesh_attr(NL80211_MESHCONF_RSSI_THRESHOLD, mask)) {
> + ? ? ? ? ? ? ? /* our RSSI threshold implementation is supported only for
> + ? ? ? ? ? ? ? ?* devices that report signal in dBm.
> + ? ? ? ? ? ? ? ?*/
> + ? ? ? ? ? ? ? if (!(sdata->local->hw.flags & IEEE80211_HW_SIGNAL_DBM))
> + ? ? ? ? ? ? ? ? ? ? ? return -ENOTSUPP;
> + ? ? ? ? ? ? ? conf->rssi_threshold = nconf->rssi_threshold;
> + ? ? ? }
> ? ? ? ?return 0;
> ?}
>
> diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
> index 510ed1d..9f484d8 100644
> --- a/net/mac80211/debugfs_netdev.c
> +++ b/net/mac80211/debugfs_netdev.c
> @@ -443,6 +443,7 @@ IEEE80211_IF_FILE(dot11MeshGateAnnouncementProtocol,
> ?IEEE80211_IF_FILE(dot11MeshHWMPRannInterval,
> ? ? ? ? ? ? ? ?u.mesh.mshcfg.dot11MeshHWMPRannInterval, DEC);
> ?IEEE80211_IF_FILE(dot11MeshForwarding, u.mesh.mshcfg.dot11MeshForwarding, DEC);
> +IEEE80211_IF_FILE(rssi_threshold, u.mesh.mshcfg.rssi_threshold, DEC);
> ?#endif
>
>
> @@ -581,6 +582,7 @@ static void add_mesh_config(struct ieee80211_sub_if_data *sdata)
> ? ? ? ?MESHPARAMS_ADD(dot11MeshHWMPRootMode);
> ? ? ? ?MESHPARAMS_ADD(dot11MeshHWMPRannInterval);
> ? ? ? ?MESHPARAMS_ADD(dot11MeshGateAnnouncementProtocol);
> + ? ? ? MESHPARAMS_ADD(rssi_threshold);
> ?#undef MESHPARAMS_ADD
> ?}
> ?#endif
> diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
> index 8806e5e..4e53c4c 100644
> --- a/net/mac80211/mesh_plink.c
> +++ b/net/mac80211/mesh_plink.c
> @@ -31,6 +31,12 @@
> ?#define dot11MeshHoldingTimeout(s) (s->u.mesh.mshcfg.dot11MeshHoldingTimeout)
> ?#define dot11MeshMaxPeerLinks(s) (s->u.mesh.mshcfg.dot11MeshMaxPeerLinks)
>
> +/* We only need a valid sta if user configured a minimum rssi_threshold. */
> +#define rssi_threshold_check(sta, sdata) \
> + ? ? ? ? ? ? ? (sdata->u.mesh.mshcfg.rssi_threshold == 0 ||\
> + ? ? ? ? ? ? ? (sta && (s8) -ewma_read(&sta->avg_signal) > \
> + ? ? ? ? ? ? ? sdata->u.mesh.mshcfg.rssi_threshold))
> +
> ?enum plink_event {
> ? ? ? ?PLINK_UNDEFINED,
> ? ? ? ?OPN_ACPT,
> @@ -301,7 +307,8 @@ void mesh_neighbour_update(u8 *hw_addr, u32 rates,
> ? ? ? ?if (mesh_peer_accepts_plinks(elems) &&
> ? ? ? ? ? ? ? ? ? ? ? ?sta->plink_state == NL80211_PLINK_LISTEN &&
> ? ? ? ? ? ? ? ? ? ? ? ?sdata->u.mesh.accepting_plinks &&
> - ? ? ? ? ? ? ? ? ? ? ? sdata->u.mesh.mshcfg.auto_open_plinks)
> + ? ? ? ? ? ? ? ? ? ? ? sdata->u.mesh.mshcfg.auto_open_plinks &&
> + ? ? ? ? ? ? ? ? ? ? ? rssi_threshold_check(sta, sdata))
> ? ? ? ? ? ? ? ?mesh_plink_open(sta);
>
> ? ? ? ?rcu_read_unlock();
> @@ -531,6 +538,14 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata, struct ieee80211_m
> ? ? ? ? ? ? ? ?return;
> ? ? ? ?}
>
> + ? ? ? if (ftype == WLAN_SP_MESH_PEERING_OPEN &&
> + ? ? ? ? ? !rssi_threshold_check(sta, sdata)) {
> + ? ? ? ? ? ? ? mpl_dbg("Mesh plink: %pM does not meet rssi threshold\n",
> + ? ? ? ? ? ? ? ? ? ? ? mgmt->sa);
> + ? ? ? ? ? ? ? rcu_read_unlock();
> + ? ? ? ? ? ? ? return;
> + ? ? ? }
> +
> ? ? ? ?if (sta && !test_sta_flag(sta, WLAN_STA_AUTH)) {
> ? ? ? ? ? ? ? ?mpl_dbg("Mesh plink: Action frame from non-authed peer\n");
> ? ? ? ? ? ? ? ?rcu_read_unlock();
> diff --git a/net/wireless/mesh.c b/net/wireless/mesh.c
> index 9d3e3b6..ba21ab2 100644
> --- a/net/wireless/mesh.c
> +++ b/net/wireless/mesh.c
> @@ -23,6 +23,8 @@
> ?#define MESH_PERR_MIN_INT ? ? ?100
> ?#define MESH_DIAM_TRAVERSAL_TIME 50
>
> +#define MESH_RSSI_THRESHOLD ? ?0
> +
> ?/*
> ?* A path will be refreshed if it is used PATH_REFRESH_TIME milliseconds
> ?* before timing out. ?This way it will remain ACTIVE and no data frames
> @@ -56,6 +58,7 @@ const struct mesh_config default_mesh_config = {
> ? ? ? ?.dot11MeshHWMPRannInterval = MESH_RANN_INTERVAL,
> ? ? ? ?.dot11MeshGateAnnouncementProtocol = false,
> ? ? ? ?.dot11MeshForwarding = true,
> + ? ? ? .rssi_threshold = MESH_RSSI_THRESHOLD,
> ?};
>
> ?const struct mesh_setup default_mesh_setup = {
> diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
> index 1998c36..25a470a 100644
> --- a/net/wireless/nl80211.c
> +++ b/net/wireless/nl80211.c
> @@ -3290,6 +3290,8 @@ static int nl80211_get_mesh_config(struct sk_buff *skb,
> ? ? ? ? ? ? ? ? ? ? ? ?cur_params.dot11MeshGateAnnouncementProtocol);
> ? ? ? ?NLA_PUT_U8(msg, NL80211_MESHCONF_FORWARDING,
> ? ? ? ? ? ? ? ? ? ? ? ?cur_params.dot11MeshForwarding);
> + ? ? ? NLA_PUT_U32(msg, NL80211_MESHCONF_RSSI_THRESHOLD,
> + ? ? ? ? ? ? ? ? ? ? ? cur_params.rssi_threshold);
> ? ? ? ?nla_nest_end(msg, pinfoattr);
> ? ? ? ?genlmsg_end(msg, hdr);
> ? ? ? ?return genlmsg_reply(msg, info);
> @@ -3322,6 +3324,7 @@ static const struct nla_policy nl80211_meshconf_params_policy[NL80211_MESHCONF_A
> ? ? ? ?[NL80211_MESHCONF_HWMP_RANN_INTERVAL] = { .type = NLA_U16 },
> ? ? ? ?[NL80211_MESHCONF_GATE_ANNOUNCEMENTS] = { .type = NLA_U8 },
> ? ? ? ?[NL80211_MESHCONF_FORWARDING] = { .type = NLA_U8 },
> + ? ? ? [NL80211_MESHCONF_RSSI_THRESHOLD] = { .type = NLA_U32},
> ?};
>
> ?static const struct nla_policy
> @@ -3413,6 +3416,8 @@ do {\
> ? ? ? ? ? ? ? ? ? ? ? ?nla_get_u8);
> ? ? ? ?FILL_IN_MESH_PARAM_IF_SET(tb, cfg, dot11MeshForwarding,
> ? ? ? ? ? ? ? ? ? ? ? ?mask, NL80211_MESHCONF_FORWARDING, nla_get_u8);
> + ? ? ? FILL_IN_MESH_PARAM_IF_SET(tb, cfg, rssi_threshold,
> + ? ? ? ? ? ? ? ? ? ? ? mask, NL80211_MESHCONF_RSSI_THRESHOLD, nla_get_u32);
> ? ? ? ?if (mask_out)
> ? ? ? ? ? ? ? ?*mask_out = mask;
>
> --
> 1.7.5.4
>
On Tue, Mar 06, 2012 at 11:23:30AM -0800, Ashok Nagarajan wrote:
> Mesh peer links are established only if average rssi of the peer
> candidate satisfies the threshold. This is not in 802.11s specification
> but was requested by David Fulgham, an open80211s user. This is a way to avoid
> marginal peer links with stations that are barely within range.
>
> This patch adds a new mesh configuration parameter, mesh_rssi_threshold. This
> feature is supported only for hardwares that report signal in dBm.
>
> Signed-off-by: Ashok Nagarajan <[email protected]>
> Signed-off-by: Javier Cardona <[email protected]>
> ---
> v3:
> use s32 instead of int32_t (Kalle Valo)
> Feature to be supported for devices reporting signal in dBm (Johannes)
>
> v4:
> Fix potential null pointer deferencing (Dan Carpenter)
I already merged v3 yesterday -- can you rework this as a fix instead?
John
--
John W. Linville Someday the world will need a hero, and you
[email protected] might be all we have. Be ready.