route/link: add bonding parser/getters and lacp rate api

[eguillaume-kalray]

Enables getting attributes from bonding interfaces.

[KanjiMonster]

Maybe also fix the style here

Suggested change

	extern uint8_t rtnl_link_bond_get_hashing_type (struct rtnl_link *link);
	extern int rtnl_link_bond_get_hashing_type(struct rtnl_link *link, uint8_t *type);

[thom311]

I also think so. Only returning uint8_t leaves no space to signal an error (or a missing attribute -NLE_NOATTR).

If the value itself is a uint8_t, then we could still do

int rtnl_link_bond_get_hashing_type (struct rtnl_link *link);

where negative values are error codes and non-negative values are the uint8_t value.

For uint32_t types, that doesn't work. So it needs

extern int rtnl_link_bond_get_miimon(struct rtnl_link *link, uint32_t *miimon);

to separately signal the error/NOATTR and the value.

I think int rtnl_link_bond_get_hashing_type (struct rtnl_link *link); is still less convenient to use, because you need

    r = rtnl_link_bond_get_hashing_type(link);
    if (r >= 0)
         hashing_type = r;
    else {
          /* handle error */
    }

instead of

     r = rtnl_link_bond_get_hashing_type(link, &hashing_type);
     if (r < 0) {
         /* handle error */
     }

So just have getters return an int (zero or negative error code) and the out value separately. Ensure that the out value is touched, if-and-only-if there is no error.

[KanjiMonster]

likewise

Suggested change

	extern uint32_t rtnl_link_bond_get_miimon (struct rtnl_link *link);
	extern int rtnl_link_bond_get_miimon(struct rtnl_link *link, uint32_t *miimon);

[KanjiMonster]

The usual way for these is to return an int, and store the value in a pointer passed as argument, so you can actually return error values if the value isn't set.

Suggested change

	extern int rtnl_link_bond_get_activeslave(struct rtnl_link *link);
	extern int rtnl_link_bond_get_activeslave(struct rtnl_link *link, int *active_slave);

E.g. activeslave wouldn't exist for an LACP bond, so we should return an error here.

[KanjiMonster]

Alphabetical order?

[KanjiMonster]

Suggested change

	extern uint32_t rtnl_link_bond_get_min_links (struct rtnl_link *link);
	extern int rtnl_link_bond_get_min_links(struct rtnl_link *link, uint32_t *min_links);

[KanjiMonster]

Suggested change

	extern uint8_t rtnl_link_bond_get_lacp_rate(struct rtnl_link *link);
	extern int rtnl_link_bond_get_lacp_rate(struct rtnl_link *link, uint8_t *lacp_rate);

[thom311]

(setting flag for "Request changes")

[KanjiMonster]

To get this moving in this I decided to push my changes I had already prepared a while ago while I was waiting for the 3.10 release with #401.