Hi Hangbin, thanks for your time. Please see below.
On Thu, 3 Aug 2023 17:30:28 +0800 Hangbin Liu liuhangbin@gmail.com wrote:
On Mon, Jul 31, 2023 at 07:51:16PM +0200, Andrea Mayer wrote:
+/* Processing of SRv6 End, End.X, and End.T behaviors can be extended through
- the flavors framework. These behaviors must report the subset of (flavor)
- operations they currently implement. In this way, if a user specifies a
- flavor combination that is not supported by a given End* behavior, the
- kernel refuses to instantiate the tunnel reporting the error.
- */
+static int seg6_flv_supp_ops_by_action(int action, __u32 *fops) +{
- switch (action) {
- case SEG6_LOCAL_ACTION_END:
*fops = SEG6_LOCAL_END_FLV_SUPP_OPS;break;- case SEG6_LOCAL_ACTION_END_X:
*fops = SEG6_LOCAL_END_X_FLV_SUPP_OPS;break;- default:
return -EOPNOTSUPP;- }
- return 0;
}
...
@@ -2070,7 +2131,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt, { struct seg6_flavors_info *finfo = &slwt->flv_info; struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
- unsigned long fops;
- int action = slwt->action;
- __u32 fops, supp_fops = 0; int rc;
rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX, @@ -2086,7 +2148,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt, return -EINVAL; fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
- if (fops & ~SEG6_LOCAL_FLV_SUPP_OPS) {
- rc = seg6_flv_supp_ops_by_action(action, &supp_fops);
- if (rc < 0 || !supp_fops || (fops & ~supp_fops)) {
if rc == 0, the supp_fops won't be 0.
Yes, you're right.
In this patch, supp_fops is always set properly when rc == 0. Since seg6_flv_supp_ops_by_action() should be extended in the event that other behaviors receive flavors support, I added this check in case the "supp_fops" field was set incorrectly or not set at all. Note that supp_fops == 0 must be considered an inadmissible value.
So, I think we have two possibilities: i) remove this "defensive" check, assuming that supp_fops will always be set correctly by seg6_flv_supp_ops_by_action() (when rc == 0, like in this patch); ii) improve the check by explicitly indicating with a pr_warn_once, for example, the condition that is occurring is unexpected.
for (ii), something like this:
parse_nla_flavors(...) { [...] supp_fops = 0; [...]
rc = seg6_flv_supp_ops_by_action(action, &supp_fops); if (!rc && !supp_fops) { /* supported flavors mask cannot be zero as it is considered to * be invalid. */ pr_warn_once("seg6local: invalid Flavor operation(s)"); return -EINVAL; }
fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]); if (rc < 0 || (fops & ~supp_fops)) { NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)"); return -EOPNOTSUPP; }
finfo->flv_ops = fops;
[...] }
parse_nla_flavors() is called in the control path so another check would not hit performance. I am more inclined to consider solution (ii).
What do you think?
Thanks Hangbin
Ciao, Andrea