TCP connection in suspend (to RAM)

TCP connection in suspend (to RAM)

[Johannes Berg]

Hi,

I'm working on a feature by which our device (Intel WiFi) will establish
a TCP connection while the host is asleep, in order to receive a wakeup
signal over the connection. There are a few configuration parameters,
but it's basically pretty simple, it establishes a connection, sending
configurable data in a configurable interval on it and wakes up the host
if it receives (certain) data on the connection or the connection breaks
(or we get disconnected from the AP, yadda yadda.)

The implementation is complex, but I've narrowed the configuration down
to configuring the IP addresses (v4 only), ports, and the data related
parameters like the interval etc.

I have two questions:
 1) I'm currently making userspace configure the destination/gateway MAC
    address. I could look up the route at configuration time, but it
    might have changed by the time we suspend and use it. At suspend
    time, I can no longer look up the route since that might require ARP
    queries. Does that seem reasonable, or is there a trick I could use?

 2) I'm making userspace configure the source port, and while some
    special cases might want this it seems like normally the kernel
    should pick an unused port. Does it seem acceptable to create a
    socket at configuration time, use inet_csk_get_port() to get an
    unused port and hang on to it until the configuration is removed
    again some time later (after suspend/resume)?

Thanks,
johannes

Re: TCP connection in suspend (to RAM)

[Johannes Berg]

On Mon, 2013-01-28 at 12:55 +0100, Johannes Berg wrote:

>  2) I'm making userspace configure the source port, and while some
>     special cases might want this it seems like normally the kernel
>     should pick an unused port. Does it seem acceptable to create a
>     socket at configuration time, use inet_csk_get_port() to get an
>     unused port and hang on to it until the configuration is removed
>     again some time later (after suspend/resume)?

Ok so let's get the question down to something technical -- Does the
below seem like a reasonable use of the socket APIs?

johannes

--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -19,6 +19,7 @@
 #include <net/genetlink.h>
 #include <net/cfg80211.h>
 #include <net/sock.h>
+#include <net/inet_connection_sock.h>
 #include "core.h"
 #include "nl80211.h"
 #include "reg.h"
@@ -7104,7 +7105,6 @@ static int nl80211_parse_wowlan_tcp(struct cfg80211_registered_device *rdev,
 	if (!tb[NL80211_WOWLAN_TCP_SRC_IPV4] ||
 	    !tb[NL80211_WOWLAN_TCP_DST_IPV4] ||
 	    !tb[NL80211_WOWLAN_TCP_DST_MAC] ||
-	    !tb[NL80211_WOWLAN_TCP_SRC_PORT] ||
 	    !tb[NL80211_WOWLAN_TCP_DST_PORT] ||
 	    !tb[NL80211_WOWLAN_TCP_DATA_PAYLOAD] ||
 	    !tb[NL80211_WOWLAN_TCP_DATA_INTERVAL] ||
@@ -7170,7 +7170,24 @@ static int nl80211_parse_wowlan_tcp(struct cfg80211_registered_device *rdev,
 	cfg->dst = nla_get_be32(tb[NL80211_WOWLAN_TCP_DST_IPV4]);
 	memcpy(cfg->dst_mac, nla_data(tb[NL80211_WOWLAN_TCP_DST_MAC]),
 	       ETH_ALEN);
-	cfg->src_port = nla_get_u16(tb[NL80211_WOWLAN_TCP_SRC_PORT]);
+	if (tb[NL80211_WOWLAN_TCP_SRC_PORT]) {
+		cfg->src_port = nla_get_u16(tb[NL80211_WOWLAN_TCP_SRC_PORT]);
+	} else {
+		/* allocate a socket and port for it and use it */
+		err = __sock_create(wiphy_net(&rdev->wiphy), PF_INET, SOCK_STREAM,
+				    IPPROTO_TCP, &cfg->sock, 1);
+		if (err) {
+			kfree(cfg);
+			return err;
+		}
+		if (inet_csk_get_port(cfg->sock->sk, 0)) {
+			sock_release(cfg->sock);
+			kfree(cfg);
+			return -ENOSPC;
+		}
+		cfg->src_port = inet_sk(cfg->sock->sk)->inet_num;
+		printk(KERN_DEBUG "allocated socket with port %d\n", cfg->src_port);
+	}
 	cfg->dst_port = nla_get_u16(tb[NL80211_WOWLAN_TCP_DST_PORT]);
 	cfg->payload_len = data_size;
 	cfg->payload = (u8 *)cfg + sizeof(*cfg) + tokens_size;
@@ -7354,6 +7371,8 @@ static int nl80211_set_wowlan(struct sk_buff *skb, struct genl_info *info)
 	for (i = 0; i < new_triggers.n_patterns; i++)
 		kfree(new_triggers.patterns[i].mask);
 	kfree(new_triggers.patterns);
+	if (new_triggers.tcp && new_triggers.tcp->sock)
+		sock_release(new_triggers.tcp->sock);
 	kfree(new_triggers.tcp);
 	return err;
 }
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -19,6 +19,7 @@
 #include <linux/nl80211.h>
 #include <linux/if_ether.h>
 #include <linux/ieee80211.h>
+#include <linux/net.h>
 #include <net/regulatory.h>
 
 /**
@@ -1576,6 +1577,7 @@ struct cfg80211_wowlan_trig_pkt_pattern {
 /**
  * struct cfg80211_wowlan_tcp - TCP connection parameters
  *
+ * @sk: (internal) port allocated if source port was automatically selected
  * @src: source IP address
  * @dst: destination IP address
  * @dst_mac: destination MAC address
@@ -1592,6 +1594,7 @@ struct cfg80211_wowlan_trig_pkt_pattern {
  * @payload_tok: payload token usage configuration
  */
 struct cfg80211_wowlan_tcp {
+	struct socket *sock;
 	__be32 src, dst;
 	u16 src_port, dst_port;
 	u8 dst_mac[ETH_ALEN];
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -3092,7 +3092,8 @@ struct nl80211_wowlan_tcp_data_token_feature {
  *	route lookup when configured might be invalid by the time we suspend,
  *	and doing a route lookup when suspending is no longer possible as it
  *	might require ARP querying.
- * @NL80211_WOWLAN_TCP_SRC_PORT: source port (u16)
+ * @NL80211_WOWLAN_TCP_SRC_PORT: source port (u16); optional, if not given a
+ *	socket and port will be allocated
  * @NL80211_WOWLAN_TCP_DST_PORT: destination port (u16)
  * @NL80211_WOWLAN_TCP_DATA_PAYLOAD: data packet payload, at least one byte.
  *	For feature advertising, a u32 attribute holding the maximum length
--- a/net/wireless/core.h
+++ b/net/wireless/core.h
@@ -109,6 +109,8 @@ cfg80211_rdev_free_wowlan(struct cfg80211_registered_device *rdev)
 	for (i = 0; i < rdev->wowlan->n_patterns; i++)
 		kfree(rdev->wowlan->patterns[i].mask);
 	kfree(rdev->wowlan->patterns);
+	if (rdev->wowlan->tcp && rdev->wowlan->tcp->sock)
+		sock_release(rdev->wowlan->tcp->sock);
 	kfree(rdev->wowlan->tcp);
 	kfree(rdev->wowlan);
 }


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