* [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister
@ 2019-09-05 4:00 wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 1/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_chain function wenxu
` (4 more replies)
0 siblings, 5 replies; 9+ messages in thread
From: wenxu @ 2019-09-05 4:00 UTC (permalink / raw)
To: pablo; +Cc: netfilter-devel
From: wenxu <wenxu@ucloud.cn>
This series clean the offload things for both chain and rules when the
related device unregister
This version add a nft_offload_netdev_iterate common function
wenxu (4):
netfilter: nf_tables_offload: refactor the nft_flow_offload_chain
function
netfilter: nf_tables_offload: refactor the nft_flow_offload_rule
function
netfilter: nf_tables_offload: add nft_offload_netdev_iterate function
netfilter: nf_tables_offload: clean offload things when the device
unregister
include/net/netfilter/nf_tables_offload.h | 2 +-
net/netfilter/nf_tables_api.c | 9 ++-
net/netfilter/nf_tables_offload.c | 122 ++++++++++++++++++++++++------
3 files changed, 105 insertions(+), 28 deletions(-)
--
1.8.3.1
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH nf-next v3 1/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_chain function
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
@ 2019-09-05 4:00 ` wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 2/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_rule function wenxu
` (3 subsequent siblings)
4 siblings, 0 replies; 9+ messages in thread
From: wenxu @ 2019-09-05 4:00 UTC (permalink / raw)
To: pablo; +Cc: netfilter-devel
From: wenxu <wenxu@ucloud.cn>
Refactor nft_flow_offload_chain and make it more common
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
v3: no change
net/netfilter/nf_tables_offload.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 3f49fe8..9419486 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -273,10 +273,9 @@ static int nft_indr_block_offload_cmd(struct nft_base_chain *chain,
#define FLOW_SETUP_BLOCK TC_SETUP_BLOCK
-static int nft_flow_offload_chain(struct nft_trans *trans,
+static int nft_flow_offload_chain(struct nft_chain *chain,
enum flow_block_command cmd)
{
- struct nft_chain *chain = trans->ctx.chain;
struct nft_base_chain *basechain;
struct net_device *dev;
@@ -288,16 +287,24 @@ static int nft_flow_offload_chain(struct nft_trans *trans,
if (!dev)
return -EOPNOTSUPP;
+ if (dev->netdev_ops->ndo_setup_tc)
+ return nft_block_offload_cmd(basechain, dev, cmd);
+ else
+ return nft_indr_block_offload_cmd(basechain, dev, cmd);
+}
+
+static int nft_flow_offload_chain_commit(struct nft_trans *trans,
+ enum flow_block_command cmd)
+{
+ struct nft_chain *chain = trans->ctx.chain;
+
/* Only default policy to accept is supported for now. */
if (cmd == FLOW_BLOCK_BIND &&
nft_trans_chain_policy(trans) != -1 &&
nft_trans_chain_policy(trans) != NF_ACCEPT)
return -EOPNOTSUPP;
- if (dev->netdev_ops->ndo_setup_tc)
- return nft_block_offload_cmd(basechain, dev, cmd);
- else
- return nft_indr_block_offload_cmd(basechain, dev, cmd);
+ return nft_flow_offload_chain(chain, cmd);
}
int nft_flow_rule_offload_commit(struct net *net)
@@ -314,13 +321,13 @@ int nft_flow_rule_offload_commit(struct net *net)
if (!(trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD))
continue;
- err = nft_flow_offload_chain(trans, FLOW_BLOCK_BIND);
+ err = nft_flow_offload_chain_commit(trans, FLOW_BLOCK_BIND);
break;
case NFT_MSG_DELCHAIN:
if (!(trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD))
continue;
- err = nft_flow_offload_chain(trans, FLOW_BLOCK_UNBIND);
+ err = nft_flow_offload_chain_commit(trans, FLOW_BLOCK_UNBIND);
break;
case NFT_MSG_NEWRULE:
if (!(trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD))
--
1.8.3.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH nf-next v3 2/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_rule function
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 1/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_chain function wenxu
@ 2019-09-05 4:00 ` wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function wenxu
` (2 subsequent siblings)
4 siblings, 0 replies; 9+ messages in thread
From: wenxu @ 2019-09-05 4:00 UTC (permalink / raw)
To: pablo; +Cc: netfilter-devel
From: wenxu <wenxu@ucloud.cn>
Refactor nft_flow_offload_rule and make it more common
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
v3: no change
net/netfilter/nf_tables_offload.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 9419486..9657001 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -134,20 +134,20 @@ int nft_chain_offload_priority(struct nft_base_chain *basechain)
return 0;
}
-static int nft_flow_offload_rule(struct nft_trans *trans,
+static int nft_flow_offload_rule(struct nft_chain *chain,
+ struct nft_rule *rule,
+ struct nft_flow_rule *flow,
enum flow_cls_command command)
{
- struct nft_flow_rule *flow = nft_trans_flow_rule(trans);
- struct nft_rule *rule = nft_trans_rule(trans);
struct flow_cls_offload cls_flow = {};
struct nft_base_chain *basechain;
struct netlink_ext_ack extack;
__be16 proto = ETH_P_ALL;
- if (!nft_is_base_chain(trans->ctx.chain))
+ if (!nft_is_base_chain(chain))
return -EOPNOTSUPP;
- basechain = nft_base_chain(trans->ctx.chain);
+ basechain = nft_base_chain(chain);
if (flow)
proto = flow->proto;
@@ -162,6 +162,16 @@ static int nft_flow_offload_rule(struct nft_trans *trans,
return nft_setup_cb_call(basechain, TC_SETUP_CLSFLOWER, &cls_flow);
}
+static int nft_flow_offload_rule_commit(struct nft_trans *trans,
+ enum flow_cls_command command)
+{
+ struct nft_flow_rule *flow = nft_trans_flow_rule(trans);
+ struct nft_rule *rule = nft_trans_rule(trans);
+ struct nft_chain *chain = trans->ctx.chain;
+
+ return nft_flow_offload_rule(chain, rule, flow, command);
+}
+
static int nft_flow_offload_bind(struct flow_block_offload *bo,
struct nft_base_chain *basechain)
{
@@ -337,14 +347,14 @@ int nft_flow_rule_offload_commit(struct net *net)
!(trans->ctx.flags & NLM_F_APPEND))
return -EOPNOTSUPP;
- err = nft_flow_offload_rule(trans, FLOW_CLS_REPLACE);
+ err = nft_flow_offload_rule_commit(trans, FLOW_CLS_REPLACE);
nft_flow_rule_destroy(nft_trans_flow_rule(trans));
break;
case NFT_MSG_DELRULE:
if (!(trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD))
continue;
- err = nft_flow_offload_rule(trans, FLOW_CLS_DESTROY);
+ err = nft_flow_offload_rule_commit(trans, FLOW_CLS_DESTROY);
break;
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 1/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_chain function wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 2/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_rule function wenxu
@ 2019-09-05 4:00 ` wenxu
2019-09-06 0:34 ` Pablo Neira Ayuso
2019-09-05 4:00 ` [PATCH nf-next v3 4/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
2019-09-06 0:27 ` [PATCH nf-next v3 0/4] " Pablo Neira Ayuso
4 siblings, 1 reply; 9+ messages in thread
From: wenxu @ 2019-09-05 4:00 UTC (permalink / raw)
To: pablo; +Cc: netfilter-devel
From: wenxu <wenxu@ucloud.cn>
Add nft_offload_netdev_iterate function. It make code more common
and can be used for others.
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
v3: new patch
net/netfilter/nf_tables_offload.c | 32 +++++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 9657001..e5977cf 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -365,16 +365,13 @@ int nft_flow_rule_offload_commit(struct net *net)
return err;
}
-static void nft_indr_block_cb(struct net_device *dev,
- flow_indr_block_bind_cb_t *cb, void *cb_priv,
- enum flow_block_command cmd)
+static struct nft_chain *nft_offload_netdev_iterate(struct net_device *dev)
{
struct nft_base_chain *basechain;
struct net *net = dev_net(dev);
- const struct nft_table *table;
- const struct nft_chain *chain;
+ struct nft_chain *chain;
+ struct nft_table *table;
- mutex_lock(&net->nft.commit_mutex);
list_for_each_entry(table, &net->nft.tables, list) {
if (table->family != NFPROTO_NETDEV)
continue;
@@ -388,11 +385,28 @@ static void nft_indr_block_cb(struct net_device *dev,
if (strncmp(basechain->dev_name, dev->name, IFNAMSIZ))
continue;
- nft_indr_block_ing_cmd(dev, basechain, cb, cb_priv, cmd);
- mutex_unlock(&net->nft.commit_mutex);
- return;
+ return chain;
}
}
+
+ return NULL;
+}
+
+static void nft_indr_block_cb(struct net_device *dev,
+ flow_indr_block_bind_cb_t *cb, void *cb_priv,
+ enum flow_block_command cmd)
+{
+ struct net *net = dev_net(dev);
+ struct nft_chain *chain;
+
+ mutex_lock(&net->nft.commit_mutex);
+ chain = nft_offload_netdev_iterate(dev);
+ if (chain) {
+ struct nft_base_chain *basechain;
+
+ basechain = nft_base_chain(chain);
+ nft_indr_block_ing_cmd(dev, basechain, cb, cb_priv, cmd);
+ }
mutex_unlock(&net->nft.commit_mutex);
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH nf-next v3 4/4] netfilter: nf_tables_offload: clean offload things when the device unregister
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
` (2 preceding siblings ...)
2019-09-05 4:00 ` [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function wenxu
@ 2019-09-05 4:00 ` wenxu
2019-09-06 0:27 ` [PATCH nf-next v3 0/4] " Pablo Neira Ayuso
4 siblings, 0 replies; 9+ messages in thread
From: wenxu @ 2019-09-05 4:00 UTC (permalink / raw)
To: pablo; +Cc: netfilter-devel
From: wenxu <wenxu@ucloud.cn>
When the net_device unregister, the netdevice_notifier will release
the related netdev basedchain and rules in this chains. So it is also
need to clean the offload things before the chain is destroy.
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
v3: make use the patch 3
include/net/netfilter/nf_tables_offload.h | 2 +-
net/netfilter/nf_tables_api.c | 9 +++++--
net/netfilter/nf_tables_offload.c | 43 ++++++++++++++++++++++++++++++-
3 files changed, 50 insertions(+), 4 deletions(-)
diff --git a/include/net/netfilter/nf_tables_offload.h b/include/net/netfilter/nf_tables_offload.h
index 643152f..acb6621 100644
--- a/include/net/netfilter/nf_tables_offload.h
+++ b/include/net/netfilter/nf_tables_offload.h
@@ -80,7 +80,7 @@ void nft_indr_block_get_and_ing_cmd(struct net_device *dev,
int nft_chain_offload_priority(struct nft_base_chain *basechain);
-void nft_offload_init(void);
+int nft_offload_init(void);
void nft_offload_exit(void);
#endif
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index a3d7e82..3c64b32 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -7691,15 +7691,20 @@ static int __init nf_tables_module_init(void)
if (err < 0)
goto err4;
+ err = nft_offload_init();
+ if (err < 0)
+ goto err5;
+
/* must be last */
err = nfnetlink_subsys_register(&nf_tables_subsys);
if (err < 0)
- goto err5;
+ goto err6;
nft_chain_route_init();
- nft_offload_init();
return err;
+err6:
+ nft_offload_exit();
err5:
rhltable_destroy(&nft_objname_ht);
err4:
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index e5977cf..20cde04 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -410,17 +410,58 @@ static void nft_indr_block_cb(struct net_device *dev,
mutex_unlock(&net->nft.commit_mutex);
}
+static void nft_offload_chain_clean(struct nft_chain *chain)
+{
+ struct nft_rule *rule;
+
+ list_for_each_entry(rule, &chain->rules, list) {
+ nft_flow_offload_rule(chain, rule,
+ NULL, FLOW_CLS_DESTROY);
+ }
+
+ nft_flow_offload_chain(chain, FLOW_BLOCK_UNBIND);
+}
+
+static int nft_offload_netdev_event(struct notifier_block *this,
+ unsigned long event, void *ptr)
+{
+ struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct net *net = dev_net(dev);
+ struct nft_chain *chain;
+
+ mutex_lock(&net->nft.commit_mutex);
+ chain = nft_offload_netdev_iterate(dev);
+ if (chain)
+ nft_offload_chain_clean(chain);
+ mutex_unlock(&net->nft.commit_mutex);
+
+ return NOTIFY_DONE;
+}
+
static struct flow_indr_block_ing_entry block_ing_entry = {
.cb = nft_indr_block_cb,
.list = LIST_HEAD_INIT(block_ing_entry.list),
};
-void nft_offload_init(void)
+static struct notifier_block nft_offload_netdev_notifier = {
+ .notifier_call = nft_offload_netdev_event,
+};
+
+int nft_offload_init(void)
{
+ int err;
+
+ err = register_netdevice_notifier(&nft_offload_netdev_notifier);
+ if (err < 0)
+ return err;
+
flow_indr_add_block_ing_cb(&block_ing_entry);
+
+ return 0;
}
void nft_offload_exit(void)
{
flow_indr_del_block_ing_cb(&block_ing_entry);
+ unregister_netdevice_notifier(&nft_offload_netdev_notifier);
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
` (3 preceding siblings ...)
2019-09-05 4:00 ` [PATCH nf-next v3 4/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
@ 2019-09-06 0:27 ` Pablo Neira Ayuso
2019-09-06 3:09 ` wenxu
4 siblings, 1 reply; 9+ messages in thread
From: Pablo Neira Ayuso @ 2019-09-06 0:27 UTC (permalink / raw)
To: wenxu; +Cc: netfilter-devel
On Thu, Sep 05, 2019 at 12:00:15PM +0800, wenxu@ucloud.cn wrote:
> From: wenxu <wenxu@ucloud.cn>
>
> This series clean the offload things for both chain and rules when the
> related device unregister
>
> This version add a nft_offload_netdev_iterate common function
>
> wenxu (4):
> netfilter: nf_tables_offload: refactor the nft_flow_offload_chain
> function
> netfilter: nf_tables_offload: refactor the nft_flow_offload_rule
> function
1/4 and 2/4 are not required anymore after adding the registration
logic to nf_tables_offload.
> netfilter: nf_tables_offload: add nft_offload_netdev_iterate function
> netfilter: nf_tables_offload: clean offload things when the device
> unregister
>
> include/net/netfilter/nf_tables_offload.h | 2 +-
> net/netfilter/nf_tables_api.c | 9 ++-
> net/netfilter/nf_tables_offload.c | 122 ++++++++++++++++++++++++------
> 3 files changed, 105 insertions(+), 28 deletions(-)
>
> --
> 1.8.3.1
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function
2019-09-05 4:00 ` [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function wenxu
@ 2019-09-06 0:34 ` Pablo Neira Ayuso
2019-09-06 3:25 ` wenxu
0 siblings, 1 reply; 9+ messages in thread
From: Pablo Neira Ayuso @ 2019-09-06 0:34 UTC (permalink / raw)
To: wenxu; +Cc: netfilter-devel
On Thu, Sep 05, 2019 at 12:00:18PM +0800, wenxu@ucloud.cn wrote:
[...]
> +static void nft_indr_block_cb(struct net_device *dev,
> + flow_indr_block_bind_cb_t *cb, void *cb_priv,
> + enum flow_block_command cmd)
> +{
> + struct net *net = dev_net(dev);
> + struct nft_chain *chain;
> +
> + mutex_lock(&net->nft.commit_mutex);
> + chain = nft_offload_netdev_iterate(dev);
Ah, right, not an interator. Probably __nft_offload_get_basechain(dev) ?
The initial __nft_... suggests the reader that the mutex is required.
> + if (chain) {
> + struct nft_base_chain *basechain;
> +
> + basechain = nft_base_chain(chain);
> + nft_indr_block_ing_cmd(dev, basechain, cb, cb_priv, cmd);
> + }
> mutex_unlock(&net->nft.commit_mutex);
> }
>
> --
> 1.8.3.1
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister
2019-09-06 0:27 ` [PATCH nf-next v3 0/4] " Pablo Neira Ayuso
@ 2019-09-06 3:09 ` wenxu
0 siblings, 0 replies; 9+ messages in thread
From: wenxu @ 2019-09-06 3:09 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel
On 9/6/2019 8:27 AM, Pablo Neira Ayuso wrote:
> On Thu, Sep 05, 2019 at 12:00:15PM +0800, wenxu@ucloud.cn wrote:
>> From: wenxu <wenxu@ucloud.cn>
>>
>> This series clean the offload things for both chain and rules when the
>> related device unregister
>>
>> This version add a nft_offload_netdev_iterate common function
>>
>> wenxu (4):
>> netfilter: nf_tables_offload: refactor the nft_flow_offload_chain
>> function
>> netfilter: nf_tables_offload: refactor the nft_flow_offload_rule
>> function
> 1/4 and 2/4 are not required anymore after adding the registration
> logic to nf_tables_offload.
Maybe it also need the 1/4 and 2/4 patches. The nft_flow_offload_chain/rule need
get some inform from the nft_trans. There is no this struct in the netdev notify event,.
So it better to refactor it more common?
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function
2019-09-06 0:34 ` Pablo Neira Ayuso
@ 2019-09-06 3:25 ` wenxu
0 siblings, 0 replies; 9+ messages in thread
From: wenxu @ 2019-09-06 3:25 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel
On 9/6/2019 8:34 AM, Pablo Neira Ayuso wrote:
> On Thu, Sep 05, 2019 at 12:00:18PM +0800, wenxu@ucloud.cn wrote:
> [...]
>> +static void nft_indr_block_cb(struct net_device *dev,
>> + flow_indr_block_bind_cb_t *cb, void *cb_priv,
>> + enum flow_block_command cmd)
>> +{
>> + struct net *net = dev_net(dev);
>> + struct nft_chain *chain;
>> +
>> + mutex_lock(&net->nft.commit_mutex);
>> + chain = nft_offload_netdev_iterate(dev);
> Ah, right, not an interator. Probably __nft_offload_get_basechain(dev) ?
>
> The initial __nft_... suggests the reader that the mutex is required.
Yes, it is better.
>
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2019-09-06 3:25 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-05 4:00 [PATCH nf-next v3 0/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 1/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_chain function wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 2/4] netfilter: nf_tables_offload: refactor the nft_flow_offload_rule function wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 3/4] netfilter: nf_tables_offload: add nft_offload_netdev_iterate function wenxu
2019-09-06 0:34 ` Pablo Neira Ayuso
2019-09-06 3:25 ` wenxu
2019-09-05 4:00 ` [PATCH nf-next v3 4/4] netfilter: nf_tables_offload: clean offload things when the device unregister wenxu
2019-09-06 0:27 ` [PATCH nf-next v3 0/4] " Pablo Neira Ayuso
2019-09-06 3:09 ` wenxu
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).