[PMTUd] add support for pmtud_get for who doesn't want notifications

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>

Author: fabbione

libknet/handle.c

@@ -792,6 +792,33 @@ int knet_handle_enable_pmtud_notify(knet_handle_t knet_h,
 	return 0;
 }
 
+int knet_handle_pmtud_get(knet_handle_t knet_h,
+			  unsigned int *link_mtu,
+			  unsigned int *data_mtu)
+{
+	int savederrno = 0;
+
+	if (!knet_h) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	savederrno = pthread_rwlock_rdlock(&knet_h->list_rwlock);
+	if (savederrno) {
+		log_err(knet_h, KNET_SUB_HANDLE, "Unable to get write lock: %s",
+			strerror(savederrno));
+		errno = savederrno;
+		return -1;
+	}
+
+	*link_mtu = knet_h->link_mtu;
+	*data_mtu = knet_h->data_mtu;
+
+	pthread_rwlock_unlock(&knet_h->list_rwlock);
+
+	return 0;
+}
+
 int knet_handle_crypto(knet_handle_t knet_h, struct knet_handle_crypto_cfg *knet_handle_crypto_cfg)
 {
 	int savederrno = 0;

libknet/libknet.h

@@ -210,6 +210,24 @@ int knet_handle_enable_pmtud_notify(knet_handle_t knet_h,
 					unsigned int link_mtu,
 					unsigned int data_mtu));
 
+/*
+ * knet_handle_pmtud_get
+ * 
+ * knet_h   - pointer to knet_handle_t
+ *
+ * link_mtu - pointer where to store link_mtu
+ * data_mtu - pointer where to store data_mtu (see above)
+ *
+ * knet_handle_pmtud_get returns:
+ *
+ * 0 on success
+ * -1 on error and errno is set.
+ */
+
+int knet_handle_pmtud_get(knet_handle_t knet_h,
+				unsigned int *link_mtu,
+				unsigned int *data_mtu);
+
 /*
  * knet_handle_crypto
  *

libknet/ping_test.c

@@ -282,6 +282,7 @@ int main(int argc, char *argv[])
 	size_t host_ids_entries = 0;
 	//int has_crypto = 0;
 	int logfd;
+	unsigned int link_mtu = 0, data_mtu = 0;
 
 	if (argc < 3) {
 		print_usage(argv[0]);
@@ -319,6 +320,13 @@ int main(int argc, char *argv[])
 		exit(EXIT_FAILURE);
 	}
 
+	if (knet_handle_pmtud_get(knet_h, &link_mtu, &data_mtu)) {
+		printf("Unable to get PMTUd current values\n");
+		exit(EXIT_FAILURE);
+	} else {
+		printf("Current PMTUd: link %u data %u\n", link_mtu, data_mtu);
+	}
+
 	if (knet_handle_enable_pmtud_notify(knet_h, pmtud_notify)) {
 		printf("Unable to install PMTUd notification callback\n");
 		exit(EXIT_FAILURE);