Server callback that selects an ALPN protocol from the client's offer.

Synopsis

Declared in <openssl/ssl.h>

typedef int(* SSL_CTX_alpn_select_cb_func)(SSL*, unsigned char const**, unsigned char*, unsigned char const*, unsigned int, void*);

Return Value

SSL_TLSEXT_ERR_OK to accept, SSL_TLSEXT_ERR_NOACK to skip ALPN, or SSL_TLSEXT_ERR_ALERT_FATAL to abort.

Parameters

Name

Description

ssl

SSL connection negotiating ALPN.

out

On success, set to the selected protocol (may point into in).

outlen

Receives the length of the selected protocol.

in

Client‐offered protocols in wire list format.

inlen

Length of in in bytes.

arg

User argument registered with SSL_CTX_set_alpn_select_cb.

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