From 5db623d98680099b25ddc37bf47ce08508071a7f Mon Sep 17 00:00:00 2001
From: Tomi Fontanilles <tomi.fontanilles@nordicsemi.no>
Date: Fri, 8 Dec 2023 11:39:33 +0200
Subject: [PATCH] lib: pdn: add function to retrieve dynamic parameters

To retrieve parameters returned by AT+CGCONTRDP=<cid>.

Signed-off-by: Tomi Fontanilles <tomi.fontanilles@nordicsemi.no>
---
 include/modem/pdn.h | 14 ++++++++++++++
 lib/pdn/pdn.c       | 30 ++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/include/modem/pdn.h b/include/modem/pdn.h
index 44830c851ddb..18923d45c516 100644
--- a/include/modem/pdn.h
+++ b/include/modem/pdn.h
@@ -10,6 +10,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <zephyr/net/net_ip.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -167,6 +168,19 @@ int pdn_deactivate(uint8_t cid);
  */
 int pdn_id_get(uint8_t cid);
 
+/**
+ * @brief Retrieves dynamic parameters of a given PDP context.
+ *
+ * @param cid The PDP context ID.
+ * @param[out] dns4_pri The address of the primary IPv4 DNS server.
+ * @param[out] dns4_sec The address of the secondary IPv4 DNS server.
+ * @param[out] ipv4_mtu The IPv4 MTU.
+ *
+ * @return Zero on success or an error code on failure.
+ */
+int pdn_dynamic_params_get(uint8_t cid, struct in_addr *dns4_pri,
+			   struct in_addr *dns4_sec, unsigned int *ipv4_mtu);
+
 /**
  * @brief Retrieve the default Access Point Name (APN).
  *
diff --git a/lib/pdn/pdn.c b/lib/pdn/pdn.c
index f59d7a5e7215..fbfd4cc87a18 100644
--- a/lib/pdn/pdn.c
+++ b/lib/pdn/pdn.c
@@ -12,6 +12,7 @@
 #include <limits.h>
 #include <zephyr/init.h>
 #include <zephyr/kernel.h>
+#include <zephyr/net/socket.h>
 #include <zephyr/sys/slist.h>
 #include <zephyr/logging/log.h>
 #include <nrf_modem_at.h>
@@ -598,6 +599,35 @@ int pdn_id_get(uint8_t cid)
 	return strtoul(p + 1, NULL, 10);
 }
 
+int pdn_dynamic_params_get(uint8_t cid, struct in_addr *dns4_pri,
+			   struct in_addr *dns4_sec, unsigned int *ipv4_mtu)
+{
+	int ret;
+	char resp[256];
+	const char *fmt;
+	char dns4_pri_str[INET_ADDRSTRLEN];
+	char dns4_sec_str[INET_ADDRSTRLEN];
+
+	ret = nrf_modem_at_cmd(resp, sizeof(resp), "AT+CGCONTRDP=%u", cid);
+	if (ret) {
+		LOG_ERR("Failed to read dynamic params for CID %u, err %d", cid, ret);
+		return ret;
+	}
+	   /* "+CGCONTRDP: 0,,"example.com","","","198.276.154.230","12.34.56.78",,,,,1464" */
+	fmt = "+CGCONTRDP: %*u,,\"%*[^\"]\",\"\",\"\",\"%15[0-9.]\",\"%15[0-9.]\",,,,,%u";
+
+	/* If IPv4 is enabled, it will be the first response line. */
+	if (sscanf(resp, fmt, &dns4_pri_str, &dns4_sec_str, ipv4_mtu) != 3) {
+		return -EBADMSG;
+	}
+
+	if (zsock_inet_pton(AF_INET, dns4_pri_str, dns4_pri) != 1
+	 || zsock_inet_pton(AF_INET, dns4_sec_str, dns4_sec) != 1) {
+		return -EFAULT;
+	}
+	return 0;
+}
+
 int pdn_default_apn_get(char *buf, size_t len)
 {
 	int err;