+
+/* This the context that we pass to alpn_cb */
+typedef struct tlsextalpnctx_st {
+ unsigned char *data;
+ unsigned short len;
+} tlsextalpnctx;
+
+static int alpn_cb(SSL *s, const unsigned char **out, unsigned char *outlen, const unsigned char *in, unsigned int inlen, void *arg)
+ {
+ tlsextalpnctx *alpn_ctx = arg;
+
+ if (!s_quiet)
+ {
+ /* We can assume that |in| is syntactically valid. */
+ unsigned i;
+ BIO_printf(bio_s_out, "ALPN protocols advertised by the client: ");
+ for (i = 0; i < inlen; )
+ {
+ if (i)
+ BIO_write(bio_s_out, ", ", 2);
+ BIO_write(bio_s_out, &in[i + 1], in[i]);
+ i += in[i] + 1;
+ }
+ BIO_write(bio_s_out, "\n", 1);
+ }
+
+ if (SSL_select_next_proto((unsigned char**) out, outlen, alpn_ctx->data, alpn_ctx->len, in, inlen) !=
+ OPENSSL_NPN_NEGOTIATED)
+ {
+ return SSL_TLSEXT_ERR_NOACK;
+ }
+
+ if (!s_quiet)
+ {
+ BIO_printf(bio_s_out, "ALPN protocols selected: ");
+ BIO_write(bio_s_out, *out, *outlen);
+ BIO_write(bio_s_out, "\n", 1);
+ }
+
+ return SSL_TLSEXT_ERR_OK;
+ }
+#endif /* ndef OPENSSL_NO_TLSEXT */