### From neon-0.27.2/src/ne_basic.h:

[...]

/* Server capabilities: */
typedef struct {
    unsigned int dav_class1; /* True if Class 1 WebDAV server */
    unsigned int dav_class2; /* True if Class 2 WebDAV server */
    unsigned int dav_executable; /* True if supports the 'executable'
				  * property a. la. mod_dav */
} ne_server_capabilities;

/* Determines server capabilities (using OPTIONS).  Pass 'path' as "*"
 * to determine proxy server capabilities if using a proxy server. */
int ne_options(ne_session *sess, const char *path,
	       ne_server_capabilities *caps);

[...]

### And now from src/ne_basic.c:

static void parse_dav_header(const char *value, ne_server_capabilities *caps)
{
    char *tokens = ne_strdup(value), *pnt = tokens;
    
    do {
	char *tok = ne_qtoken(&pnt, ',',  "\"'");
	if (!tok) break;
	
	tok = ne_shave(tok, " \r\t\n");

	if (strcmp(tok, "1") == 0) {
	    caps->dav_class1 = 1;
	} else if (strcmp(tok, "2") == 0) {
	    caps->dav_class2 = 1;
	} else if (strcmp(tok, "<http://apache.org/dav/propset/fs/1>") == 0) {
	    caps->dav_executable = 1;
	}
    } while (pnt != NULL);
    
    ne_free(tokens);
}

int ne_options(ne_session *sess, const char *uri, ne_server_capabilities *caps)
{
    ne_request *req = ne_request_create(sess, "OPTIONS", uri);
    int ret = ne_request_dispatch(req);
    const char *header = ne_get_response_header(req, "DAV");
    
    if (header) parse_dav_header(header, caps);
 
    if (ret == NE_OK && ne_get_status(req)->klass != 2) {
	ret = NE_ERROR;
    }
    
    ne_request_destroy(req);

    return ret;
}