nc_read_msg_io buf unused + don't create deleted endpoints

[jeremie6wind]

Hi,
I had these 2 issues with libnetconf 4.0.1:

First patch:
src/io.c: Sometimes I get ret = 0 and an empty buf so ly_in_new_memory failed.
I propose to return if ret is 0?

Second patch:
Replacing the netconf server endpoint may fail:
For instance if the endpoint name is ssh1, we try to replace it with an endpoint name called ssh2.
nc_server_config_listen_all_endpoints first tries to create ssh1 whereas it is supposed to be deleted.
It fails and return.
Then it does not try to create ssh2.

For instance I tried to apply these 2 configs:

<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
    <listen>
        <endpoints>
            <endpoint>
                <name>ssh1</name>
                <ssh>
                    <tcp-server-parameters>
                        <local-address>127.0.0.1</local-address>
                        <local-port>830</local-port>
                    </tcp-server-parameters>
                    <ssh-server-parameters>
                      <server-identity>
                        <host-key>
                          <name>default-key</name>
                          <public-key>
                            <central-keystore-reference>genkey</central-keystore-reference>
                          </public-key>
                        </host-key>
                      </server-identity>
                    </ssh-server-parameters>
                </ssh>
            </endpoint>
        </endpoints>
    </listen>
</netconf-server>
</config>

then:

<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<netconf-server xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
    <listen>
        <endpoints>
            <endpoint>
                <name>ssh2</name>
                <ssh>
                    <tcp-server-parameters>
                        <local-address>127.0.0.2</local-address>
			            <local-port>830</local-port>
                    </tcp-server-parameters>
                    <ssh-server-parameters>
                      <server-identity>
                        <host-key>
                          <name>default-key</name>
                          <public-key>
                            <central-keystore-reference>genkey</central-keystore-reference>
                          </public-key>
                        </host-key>
                      </server-identity>
                    </ssh-server-parameters>
                </ssh>
            </endpoint>
        </endpoints>
    </listen>
</netconf-server>
</config>

I get these errors:
[ERR]: LN: Endpoint "ssh1" was not found.
[ERR]: LN: Applying ietf-netconf-server configuration failed.

In the second patch, I tried to skip endpoints with the delete yang operation.

Thank you

[Roytak]

LGTM, just one small thing and will merge it then. Thank you.

[Roytak]

We define all variables at the beginning of the given functions.

[jlesk]

thank you