Add SNI client support

Close #1200

include/znc/Socket.h

@@ -33,6 +33,7 @@ public:
 #ifdef HAVE_LIBSSL
 	int VerifyPeerCertificate(int iPreVerify, X509_STORE_CTX * pStoreCTX) override;
 	void SSLHandShakeFinished() override;
+	bool SNIConfigureClient(CString& sHostname) override;
 #endif
 	void SetHostToVerifySSL(const CString& sHost) { m_HostToVerifySSL = sHost; }
 	CString GetSSLPeerFingerprint() const;

src/Socket.cpp

@@ -126,6 +126,11 @@ void CZNCSock::SSLHandShakeFinished() {
 	CallSockError(errnoBadSSLCert, sErrorMsg);
 	Close();
 }
+
+bool CZNCSock::SNIConfigureClient(CString& sHostname) {
+	sHostname = m_HostToVerifySSL;
+	return true;
+}
 #endif
 
 CString CZNCSock::GetSSLPeerFingerprint() const {