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unitytls: fix handling of blocked sends #33

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Merged
Petezah merged 1 commit into from
Jan 6, 2026
Merged

unitytls: fix handling of blocked sends #33

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20 changes: 20 additions & 0 deletions lib/vtls/unitytls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,8 @@ struct ssl_backend_data {
#ifdef HAS_ALPN
const char *protocols[ALPN_ENTRIES_MAX + 1];
#endif
size_t send_blocked_len;
BIT(send_blocked);
};

/*
Expand Down Expand Up @@ -310,6 +312,18 @@ static ssize_t unitytls_send(struct Curl_cfilter *cf, struct Curl_easy *data,
struct ssl_connect_data *connssl = cf->ctx;
struct ssl_backend_data *backend = connssl->backend;

/* Similar to mbedtls implementation, if unitytls_tlsctx_write was
* previously blocked, it must be called with the same amount of bytes
* again, or it will lose bytes , e.g. reporting all was sent but they
* were not. If that happens, the other side errors and hangs up.
* Remember the blocked length and use that when it is set. */
if(backend->send_blocked) {
DEBUGASSERT(backend->send_blocked_len <= len);
CURL_TRC_CF(data, cf, "unitytls_tlsctx_write(len=%zu) -> previously blocked "
"on %zu bytes", len, backend->send_blocked_len);
len = backend->send_blocked_len;
}

size_t written = 0;
unitytls_errorstate err = unitytls->unitytls_errorstate_create();
written = unitytls->unitytls_tlsctx_write(backend->ctx, (const UInt8*)mem, len, &err);
Expand All @@ -321,9 +335,15 @@ static ssize_t unitytls_send(struct Curl_cfilter *cf, struct Curl_easy *data,
*curlcode = CURLE_SEND_ERROR;
failf(data, "Sending data failed with unitytls error code %i", err.code);
}
if((*curlcode == CURLE_AGAIN) && !backend->send_blocked) {
backend->send_blocked = TRUE;
backend->send_blocked_len = len;
}
return -1;
}

CURL_TRC_CF(data, cf, "unitytls_tlsctx_write(len=%zu) -> %d", len, err.code);
backend->send_blocked = FALSE;
return written;
}

Expand Down
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