DPDK patches and discussions
 help / color / mirror / Atom feed
From: Nithin Dabilpuram <ndabilpuram@marvell.com>
To: <jerinj@marvell.com>, Nithin Dabilpuram <ndabilpuram@marvell.com>,
	"Kiran Kumar K" <kirankumark@marvell.com>,
	Sunil Kumar Kori <skori@marvell.com>,
	Satha Rao <skoteshwar@marvell.com>,
	Harman Kalra <hkalra@marvell.com>
Cc: <dev@dpdk.org>, Srujana Challa <schalla@marvell.com>
Subject: [PATCH v2 12/17] net/cnxk: add PMD APIs to submit CPT instruction
Date: Tue, 1 Oct 2024 11:30:50 +0530	[thread overview]
Message-ID: <20241001060055.3747591-12-ndabilpuram@marvell.com> (raw)
In-Reply-To: <20241001060055.3747591-1-ndabilpuram@marvell.com>

From: Srujana Challa <schalla@marvell.com>

Introduces new PMD APIs for submitting CPT instructions to the
Inline Device. These APIs allows applications to directly submit
CPT instructions to the Inline Device.

Signed-off-by: Srujana Challa <schalla@marvell.com>
---
 drivers/common/cnxk/roc_nix_inl.h      | 12 ++++++-
 drivers/common/cnxk/roc_nix_inl_dev.c  | 32 +++++++++++++++++
 drivers/common/cnxk/roc_nix_inl_priv.h |  2 ++
 drivers/common/cnxk/version.map        |  1 +
 drivers/net/cnxk/cn10k_ethdev_sec.c    | 42 ++++++++++++++++++++++
 drivers/net/cnxk/cn9k_ethdev_sec.c     | 14 ++++++++
 drivers/net/cnxk/cnxk_ethdev.c         |  1 +
 drivers/net/cnxk/cnxk_ethdev.h         | 48 ++++++++++++++++++++++++++
 drivers/net/cnxk/cnxk_ethdev_sec.c     | 19 ++++++++++
 drivers/net/cnxk/rte_pmd_cnxk.h        | 35 +++++++++++++++++++
 drivers/net/cnxk/version.map           |  2 ++
 11 files changed, 207 insertions(+), 1 deletion(-)

diff --git a/drivers/common/cnxk/roc_nix_inl.h b/drivers/common/cnxk/roc_nix_inl.h
index 1a4bf8808c..974834a0f3 100644
--- a/drivers/common/cnxk/roc_nix_inl.h
+++ b/drivers/common/cnxk/roc_nix_inl.h
@@ -99,10 +99,19 @@ struct roc_nix_inl_dev {
 	uint8_t rx_inj_ena; /* Rx Inject Enable */
 	/* End of input parameters */
 
-#define ROC_NIX_INL_MEM_SZ (1408)
+#define ROC_NIX_INL_MEM_SZ (2048)
 	uint8_t reserved[ROC_NIX_INL_MEM_SZ] __plt_cache_aligned;
 } __plt_cache_aligned;
 
+struct roc_nix_inl_dev_q {
+	uint32_t nb_desc;
+	uintptr_t rbase;
+	uintptr_t lmt_base;
+	uint64_t *fc_addr;
+	uint64_t io_addr;
+	int32_t fc_addr_sw;
+} __plt_cache_aligned;
+
 /* NIX Inline Device API */
 int __roc_api roc_nix_inl_dev_init(struct roc_nix_inl_dev *roc_inl_dev);
 int __roc_api roc_nix_inl_dev_fini(struct roc_nix_inl_dev *roc_inl_dev);
@@ -176,5 +185,6 @@ int __roc_api roc_nix_inl_ctx_write(struct roc_nix *roc_nix, void *sa_dptr,
 				    void *sa_cptr, bool inb, uint16_t sa_len);
 void __roc_api roc_nix_inl_outb_cpt_lfs_dump(struct roc_nix *roc_nix, FILE *file);
 uint64_t __roc_api roc_nix_inl_eng_caps_get(struct roc_nix *roc_nix);
+void *__roc_api roc_nix_inl_dev_qptr_get(uint8_t qid);
 
 #endif /* _ROC_NIX_INL_H_ */
diff --git a/drivers/common/cnxk/roc_nix_inl_dev.c b/drivers/common/cnxk/roc_nix_inl_dev.c
index e2bbe3a67b..84c69a44c5 100644
--- a/drivers/common/cnxk/roc_nix_inl_dev.c
+++ b/drivers/common/cnxk/roc_nix_inl_dev.c
@@ -168,6 +168,7 @@ nix_inl_nix_ipsec_cfg(struct nix_inl_dev *inl_dev, bool ena)
 static int
 nix_inl_cpt_setup(struct nix_inl_dev *inl_dev, bool inl_dev_sso)
 {
+	struct roc_nix_inl_dev_q *q_info;
 	struct dev *dev = &inl_dev->dev;
 	bool ctx_ilen_valid = false;
 	struct roc_cpt_lf *lf;
@@ -209,6 +210,13 @@ nix_inl_cpt_setup(struct nix_inl_dev *inl_dev, bool inl_dev_sso)
 			goto lf_free;
 		}
 
+		q_info = &inl_dev->q_info[i];
+		q_info->nb_desc = lf->nb_desc;
+		q_info->fc_addr = lf->fc_addr;
+		q_info->io_addr = lf->io_addr;
+		q_info->lmt_base = lf->lmt_base;
+		q_info->rbase = lf->rbase;
+
 		roc_cpt_iq_enable(lf);
 	}
 	return 0;
@@ -835,6 +843,30 @@ nix_inl_outb_poll_thread_setup(struct nix_inl_dev *inl_dev)
 	return rc;
 }
 
+void *
+roc_nix_inl_dev_qptr_get(uint8_t qid)
+{
+	struct idev_cfg *idev = idev_get_cfg();
+	struct nix_inl_dev *inl_dev = NULL;
+
+	if (idev)
+		inl_dev = idev->nix_inl_dev;
+
+	if (!inl_dev) {
+		plt_err("Inline Device could not be detected\n");
+		return NULL;
+	}
+	if (!inl_dev->attach_cptlf) {
+		plt_err("No CPT LFs are attached to Inline Device\n");
+		return NULL;
+	}
+	if (qid >= inl_dev->nb_cptlf) {
+		plt_err("Invalid qid: %u total queues: %d\n", qid, inl_dev->nb_cptlf);
+		return NULL;
+	}
+	return &inl_dev->q_info[qid];
+}
+
 int
 roc_nix_inl_dev_stats_get(struct roc_nix_stats *stats)
 {
diff --git a/drivers/common/cnxk/roc_nix_inl_priv.h b/drivers/common/cnxk/roc_nix_inl_priv.h
index 5afc7d6655..64b8b3977d 100644
--- a/drivers/common/cnxk/roc_nix_inl_priv.h
+++ b/drivers/common/cnxk/roc_nix_inl_priv.h
@@ -100,6 +100,8 @@ struct nix_inl_dev {
 	uint32_t curr_ipsec_idx;
 	uint32_t max_ipsec_rules;
 	uint32_t alloc_ipsec_rules;
+
+	struct roc_nix_inl_dev_q q_info[NIX_INL_CPT_LF];
 };
 
 int nix_inl_sso_register_irqs(struct nix_inl_dev *inl_dev);
diff --git a/drivers/common/cnxk/version.map b/drivers/common/cnxk/version.map
index f98738d07e..8832c75eef 100644
--- a/drivers/common/cnxk/version.map
+++ b/drivers/common/cnxk/version.map
@@ -267,6 +267,7 @@ INTERNAL {
 	roc_nix_inl_meta_pool_cb_register;
 	roc_nix_inl_custom_meta_pool_cb_register;
 	roc_nix_inb_mode_set;
+	roc_nix_inl_dev_qptr_get;
 	roc_nix_inl_outb_fini;
 	roc_nix_inl_outb_init;
 	roc_nix_inl_outb_lf_base_get;
diff --git a/drivers/net/cnxk/cn10k_ethdev_sec.c b/drivers/net/cnxk/cn10k_ethdev_sec.c
index 074bb09822..f22f2ae12d 100644
--- a/drivers/net/cnxk/cn10k_ethdev_sec.c
+++ b/drivers/net/cnxk/cn10k_ethdev_sec.c
@@ -1305,6 +1305,45 @@ cn10k_eth_sec_rx_inject_config(void *device, uint16_t port_id, bool enable)
 	return 0;
 }
 
+#define CPT_LMTST_BURST 32
+static uint16_t
+cn10k_inl_dev_submit(struct roc_nix_inl_dev_q *q, void *inst, uint16_t nb_inst)
+{
+	uintptr_t lbase = q->lmt_base;
+	uint8_t lnum, shft, loff;
+	uint16_t left, burst;
+	rte_iova_t io_addr;
+	uint16_t lmt_id;
+
+	/* Check the flow control to avoid the queue overflow */
+	if (cnxk_nix_inl_fc_check(q->fc_addr, &q->fc_addr_sw, q->nb_desc, nb_inst))
+		return 0;
+
+	io_addr = q->io_addr;
+	ROC_LMT_CPT_BASE_ID_GET(lbase, lmt_id);
+
+	left = nb_inst;
+again:
+	burst = left > CPT_LMTST_BURST ? CPT_LMTST_BURST : left;
+
+	lnum = 0;
+	loff = 0;
+	shft = 16;
+	memcpy(PLT_PTR_CAST(lbase), inst, burst * sizeof(struct cpt_inst_s));
+	loff = (burst % 2) ? 1 : 0;
+	lnum = (burst / 2);
+	shft = shft + (lnum * 3);
+
+	left -= burst;
+	cn10k_nix_sec_steorl(io_addr, lmt_id, lnum, loff, shft);
+	rte_io_wmb();
+	if (left) {
+		inst = RTE_PTR_ADD(inst, burst * sizeof(struct cpt_inst_s));
+		goto again;
+	}
+	return nb_inst;
+}
+
 void
 cn10k_eth_sec_ops_override(void)
 {
@@ -1341,4 +1380,7 @@ cn10k_eth_sec_ops_override(void)
 	cnxk_eth_sec_ops.macsec_sa_stats_get = cnxk_eth_macsec_sa_stats_get;
 	cnxk_eth_sec_ops.rx_inject_configure = cn10k_eth_sec_rx_inject_config;
 	cnxk_eth_sec_ops.inb_pkt_rx_inject = cn10k_eth_sec_inb_rx_inject;
+
+	/* Update platform specific rte_pmd_cnxk ops */
+	cnxk_pmd_ops.inl_dev_submit = cn10k_inl_dev_submit;
 }
diff --git a/drivers/net/cnxk/cn9k_ethdev_sec.c b/drivers/net/cnxk/cn9k_ethdev_sec.c
index a0e0a73639..ae8d04be69 100644
--- a/drivers/net/cnxk/cn9k_ethdev_sec.c
+++ b/drivers/net/cnxk/cn9k_ethdev_sec.c
@@ -845,6 +845,17 @@ cn9k_eth_sec_capabilities_get(void *device __rte_unused)
 	return cn9k_eth_sec_capabilities;
 }
 
+static uint16_t
+cn9k_inl_dev_submit(struct roc_nix_inl_dev_q *q, void *inst, uint16_t nb_inst)
+{
+	/* Not supported */
+	PLT_SET_USED(q);
+	PLT_SET_USED(inst);
+	PLT_SET_USED(nb_inst);
+
+	return 0;
+}
+
 void
 cn9k_eth_sec_ops_override(void)
 {
@@ -859,4 +870,7 @@ cn9k_eth_sec_ops_override(void)
 	cnxk_eth_sec_ops.session_update = cn9k_eth_sec_session_update;
 	cnxk_eth_sec_ops.session_destroy = cn9k_eth_sec_session_destroy;
 	cnxk_eth_sec_ops.capabilities_get = cn9k_eth_sec_capabilities_get;
+
+	/* Update platform specific rte_pmd_cnxk ops */
+	cnxk_pmd_ops.inl_dev_submit = cn9k_inl_dev_submit;
 }
diff --git a/drivers/net/cnxk/cnxk_ethdev.c b/drivers/net/cnxk/cnxk_ethdev.c
index dd065c8269..13b7e8a38c 100644
--- a/drivers/net/cnxk/cnxk_ethdev.c
+++ b/drivers/net/cnxk/cnxk_ethdev.c
@@ -135,6 +135,7 @@ nix_security_setup(struct cnxk_eth_dev *dev)
 			rc = -ENOMEM;
 			goto cleanup;
 		}
+		dev->inb.inl_dev_q = roc_nix_inl_dev_qptr_get(0);
 	}
 
 	if (dev->tx_offloads & RTE_ETH_TX_OFFLOAD_SECURITY ||
diff --git a/drivers/net/cnxk/cnxk_ethdev.h b/drivers/net/cnxk/cnxk_ethdev.h
index 5920488e1a..d4440b25ac 100644
--- a/drivers/net/cnxk/cnxk_ethdev.h
+++ b/drivers/net/cnxk/cnxk_ethdev.h
@@ -260,6 +260,9 @@ struct cnxk_eth_dev_sec_inb {
 
 	/* Disable custom meta aura */
 	bool custom_meta_aura_dis;
+
+	/* Inline device CPT queue info */
+	struct roc_nix_inl_dev_q *inl_dev_q;
 };
 
 /* Outbound security data */
@@ -499,6 +502,42 @@ cnxk_nix_tx_queue_sec_count(uint64_t *mem, uint16_t sqes_per_sqb_log2, uint64_t
 	return (val & 0xFFFF);
 }
 
+static inline int
+cnxk_nix_inl_fc_check(uint64_t *fc, int32_t *fc_sw, uint32_t nb_desc, uint16_t nb_inst)
+{
+	uint8_t retry_count = 32;
+	int32_t val, newval;
+
+	/* Check if there is any CPT instruction to submit */
+	if (!nb_inst)
+		return -EINVAL;
+
+retry:
+	val = rte_atomic_fetch_sub_explicit((RTE_ATOMIC(int32_t)*)fc_sw, nb_inst,
+					    rte_memory_order_relaxed) - nb_inst;
+	if (likely(val >= 0))
+		return 0;
+
+	newval = (int64_t)nb_desc - rte_atomic_load_explicit((RTE_ATOMIC(uint64_t)*)fc,
+							     rte_memory_order_relaxed);
+	newval -= nb_inst;
+
+	if (!rte_atomic_compare_exchange_strong_explicit((RTE_ATOMIC(int32_t)*)fc_sw, &val, newval,
+							 rte_memory_order_release,
+							 rte_memory_order_relaxed)) {
+		if (retry_count) {
+			retry_count--;
+			goto retry;
+		} else {
+			return -EAGAIN;
+		}
+	}
+	if (unlikely(newval < 0))
+		return -EAGAIN;
+
+	return 0;
+}
+
 /* Common ethdev ops */
 extern struct eth_dev_ops cnxk_eth_dev_ops;
 
@@ -511,6 +550,15 @@ extern struct rte_security_ops cnxk_eth_sec_ops;
 /* Common tm ops */
 extern struct rte_tm_ops cnxk_tm_ops;
 
+/* Platform specific rte pmd cnxk ops */
+typedef uint16_t (*cnxk_inl_dev_submit_cb_t)(struct roc_nix_inl_dev_q *q, void *inst,
+					     uint16_t nb_inst);
+
+struct cnxk_ethdev_pmd_ops {
+	cnxk_inl_dev_submit_cb_t inl_dev_submit;
+};
+extern struct cnxk_ethdev_pmd_ops cnxk_pmd_ops;
+
 /* Ops */
 int cnxk_nix_probe(struct rte_pci_driver *pci_drv,
 		   struct rte_pci_device *pci_dev);
diff --git a/drivers/net/cnxk/cnxk_ethdev_sec.c b/drivers/net/cnxk/cnxk_ethdev_sec.c
index ec129b6584..7e5103bf54 100644
--- a/drivers/net/cnxk/cnxk_ethdev_sec.c
+++ b/drivers/net/cnxk/cnxk_ethdev_sec.c
@@ -33,6 +33,8 @@ struct inl_cpt_channel {
 #define CNXK_NIX_INL_DEV_NAME_LEN                                              \
 	(sizeof(CNXK_NIX_INL_DEV_NAME) + PCI_PRI_STR_SIZE)
 
+struct cnxk_ethdev_pmd_ops cnxk_pmd_ops;
+
 static inline int
 bitmap_ctzll(uint64_t slab)
 {
@@ -297,6 +299,18 @@ cnxk_eth_sec_sess_get_by_sess(struct cnxk_eth_dev *dev,
 	return NULL;
 }
 
+uint16_t
+rte_pmd_cnxk_inl_dev_submit(struct rte_pmd_cnxk_inl_dev_q *qptr, void *inst, uint16_t nb_inst)
+{
+	return cnxk_pmd_ops.inl_dev_submit((struct roc_nix_inl_dev_q *)qptr, inst, nb_inst);
+}
+
+struct rte_pmd_cnxk_inl_dev_q *
+rte_pmd_cnxk_inl_dev_qptr_get(void)
+{
+	return roc_nix_inl_dev_qptr_get(0);
+}
+
 union rte_pmd_cnxk_ipsec_hw_sa *
 rte_pmd_cnxk_hw_session_base_get(uint16_t portid, bool inb)
 {
@@ -353,6 +367,7 @@ rte_pmd_cnxk_hw_sa_write(uint16_t portid, void *sess, union rte_pmd_cnxk_ipsec_h
 	struct rte_eth_dev *eth_dev = &rte_eth_devices[portid];
 	struct cnxk_eth_dev *dev = cnxk_eth_pmd_priv(eth_dev);
 	struct cnxk_eth_sec_sess *eth_sec;
+	struct roc_nix_inl_dev_q *q;
 	void *sa;
 
 	eth_sec = cnxk_eth_sec_sess_get_by_sess(dev, sess);
@@ -361,6 +376,10 @@ rte_pmd_cnxk_hw_sa_write(uint16_t portid, void *sess, union rte_pmd_cnxk_ipsec_h
 	else
 		sa = sess;
 
+	q = dev->inb.inl_dev_q;
+	if (q && cnxk_nix_inl_fc_check(q->fc_addr, &q->fc_addr_sw, q->nb_desc, 1))
+		return -EAGAIN;
+
 	return roc_nix_inl_ctx_write(&dev->nix, data, sa, inb, len);
 }
 
diff --git a/drivers/net/cnxk/rte_pmd_cnxk.h b/drivers/net/cnxk/rte_pmd_cnxk.h
index ecd112e881..798547e731 100644
--- a/drivers/net/cnxk/rte_pmd_cnxk.h
+++ b/drivers/net/cnxk/rte_pmd_cnxk.h
@@ -489,6 +489,13 @@ union rte_pmd_cnxk_cpt_res_s {
 	uint64_t u64[2];
 };
 
+/** Forward structure declaration for inline device queue. Applications obtain a pointer
+ * to this structure using the ``rte_pmd_cnxk_inl_dev_qptr_get`` API and use it to submit
+ * CPT instructions (cpt_inst_s) to the inline device via the
+ * ``rte_pmd_cnxk_inl_dev_submit`` API.
+ */
+struct rte_pmd_cnxk_inl_dev_q;
+
 /**
  * Read HW SA context from session.
  *
@@ -578,4 +585,32 @@ union rte_pmd_cnxk_ipsec_hw_sa *rte_pmd_cnxk_hw_session_base_get(uint16_t portid
  */
 __rte_experimental
 int rte_pmd_cnxk_sa_flush(uint16_t portid, union rte_pmd_cnxk_ipsec_hw_sa *sess, bool inb);
+
+/**
+ * Get queue pointer of Inline Device.
+ *
+ * @return
+ *   - Pointer to queue structure that would be the input to submit API.
+ *   - NULL upon failure.
+ */
+__rte_experimental
+struct rte_pmd_cnxk_inl_dev_q *rte_pmd_cnxk_inl_dev_qptr_get(void);
+
+/**
+ * Submit CPT instruction(s) (cpt_inst_s) to Inline Device.
+ *
+ * @param qptr
+ *   Pointer obtained with ``rte_pmd_cnxk_inl_dev_qptr_get``.
+ * @param inst
+ *   Pointer to an array of ``cpt_inst_s`` prapared by application.
+ * @param nb_inst
+ *   Number of instructions to be processed.
+ *
+ * @return
+ *   Number of instructions processed.
+ */
+__rte_experimental
+uint16_t rte_pmd_cnxk_inl_dev_submit(struct rte_pmd_cnxk_inl_dev_q *qptr, void *inst,
+				     uint16_t nb_inst);
+
 #endif /* _PMD_CNXK_H_ */
diff --git a/drivers/net/cnxk/version.map b/drivers/net/cnxk/version.map
index 7e8703df5c..58dcb1fac0 100644
--- a/drivers/net/cnxk/version.map
+++ b/drivers/net/cnxk/version.map
@@ -11,6 +11,8 @@ EXPERIMENTAL {
 
 	# added in 23.11
 	rte_pmd_cnxk_hw_session_base_get;
+	rte_pmd_cnxk_inl_dev_qptr_get;
+	rte_pmd_cnxk_inl_dev_submit;
 	rte_pmd_cnxk_inl_ipsec_res;
 	rte_pmd_cnxk_sa_flush;
 };
-- 
2.34.1


  parent reply	other threads:[~2024-10-01  6:02 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-01  6:00 [PATCH v2 01/17] net/cnxk: added telemetry support do dump SA information Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 02/17] net/cnxk: handle timestamp correctly for VF Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 03/17] net/cnxk: update Rx offloads to handle timestamp Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 04/17] event/cnxk: handle timestamp for event mode Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 05/17] net/cnxk: update mbuf and rearm data for Rx inject packets Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 06/17] common/cnxk: remove restriction to clear RPM stats Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 07/17] common/cnxk: allow MAC address set/add with active VFs Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 08/17] net/cnxk: move PMD function defines to common code Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 09/17] common/cnxk: add flush wait after write of inline ctx Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 10/17] common/cnxk: fix CPT HW word size for outbound SA Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 11/17] net/cnxk: add PMD APIs for IPsec SA base and flush Nithin Dabilpuram
2024-10-01  6:00 ` Nithin Dabilpuram [this message]
2024-10-01  6:00 ` [PATCH v2 13/17] net/cnxk: add PMD API to retrieve CPT queue statistics Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 14/17] net/cnxk: add option to enable custom inbound sa usage Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 15/17] net/cnxk: add PMD API to retrieve the model string Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 16/17] net/cnxk: handle OOP for inbound packet Nithin Dabilpuram
2024-10-01  6:00 ` [PATCH v2 17/17] event/cnxk: handle inbound out of place processing Nithin Dabilpuram

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20241001060055.3747591-12-ndabilpuram@marvell.com \
    --to=ndabilpuram@marvell.com \
    --cc=dev@dpdk.org \
    --cc=hkalra@marvell.com \
    --cc=jerinj@marvell.com \
    --cc=kirankumark@marvell.com \
    --cc=schalla@marvell.com \
    --cc=skori@marvell.com \
    --cc=skoteshwar@marvell.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
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).