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Date: Thu, 27 Jun 2019 14:35:27 -0500
From: Dan Williams <dcbw@...hat.com>
To: Stephen Hemminger <stephen@...workplumber.org>,
Michal Kubecek <mkubecek@...e.cz>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
David Ahern <dsahern@...il.com>, Jiri Pirko <jiri@...nulli.us>,
davem@...emloft.net, jakub.kicinski@...ronome.com,
mlxsw@...lanox.com
Subject: Re: [RFC] longer netdev names proposal
On Thu, 2019-06-27 at 12:20 -0700, Stephen Hemminger wrote:
> On Thu, 27 Jun 2019 20:39:48 +0200
> Michal Kubecek <mkubecek@...e.cz> wrote:
>
> > > $ ip li set dev enp3s0 alias "Onboard Ethernet"
> > > # ip link show "Onboard Ethernet"
> > > Device "Onboard Ethernet" does not exist.
> > >
> > > So it does not really appear to be an alias, it is a label. To be
> > > truly useful, it needs to be more than a label, it needs to be a
> > > real
> > > alias which you can use.
> >
> > That's exactly what I meant: to be really useful, one should be
> > able to
> > use the alias(es) for setting device options, for adding routes, in
> > netfilter rules etc.
> >
> > Michal
>
> The kernel doesn't enforce uniqueness of alias.
Can we even enforce unique aliases/labels? Given that the kernel hasn't
enforced that in the past there's a good possibility of breaking stuff
if it started. (unfortunately)
Dan
> Also current kernel RTM_GETLINK doesn't do filter by alias (easily
> fixed).
>
> If it did, then handling it in iproute would be something like:
>
> diff --git a/lib/ll_map.c b/lib/ll_map.c
> index e0ed54bf77c9..c798ba542224 100644
> --- a/lib/ll_map.c
> +++ b/lib/ll_map.c
> @@ -26,15 +26,18 @@
> struct ll_cache {
> struct hlist_node idx_hash;
> struct hlist_node name_hash;
> + struct hlist_node alias_hash;
> unsigned flags;
> unsigned index;
> unsigned short type;
> - char name[];
> + char *alias;
> + char name[IFNAMSIZ];
> };
>
> #define IDXMAP_SIZE 1024
> static struct hlist_head idx_head[IDXMAP_SIZE];
> static struct hlist_head name_head[IDXMAP_SIZE];
> +static struct hlist_head alias_head[IDXMAP_SIZE];
>
> static struct ll_cache *ll_get_by_index(unsigned index)
> {
> @@ -77,10 +80,26 @@ static struct ll_cache *ll_get_by_name(const char
> *name)
> return NULL;
> }
>
> +static struct ll_cache *ll_get_by_alias(const char *alias)
> +{
> + struct hlist_node *n;
> + unsigned h = namehash(alias) & (IDXMAP_SIZE - 1);
> +
> + hlist_for_each(n, &alias_head[h]) {
> + struct ll_cache *im
> + = container_of(n, struct ll_cache, alias_hash);
> +
> + if (strcmp(im->alias, alias) == 0)
> + return im;
> + }
> +
> + return NULL;
> +}
> +
> int ll_remember_index(struct nlmsghdr *n, void *arg)
> {
> unsigned int h;
> - const char *ifname;
> + const char *ifname, *ifalias;
> struct ifinfomsg *ifi = NLMSG_DATA(n);
> struct ll_cache *im;
> struct rtattr *tb[IFLA_MAX+1];
> @@ -96,6 +115,10 @@ int ll_remember_index(struct nlmsghdr *n, void
> *arg)
> if (im) {
> hlist_del(&im->name_hash);
> hlist_del(&im->idx_hash);
> + if (im->alias) {
> + hlist_del(&im->alias_hash);
> + free(im->alias);
> + }
> free(im);
> }
> return 0;
> @@ -106,6 +129,8 @@ int ll_remember_index(struct nlmsghdr *n, void
> *arg)
> if (ifname == NULL)
> return 0;
>
> + ifalias = tb[IFLA_IFALIAS] ? rta_getattr_str(tb[IFLA_IFALIAS])
> : NULL;
> +
> if (im) {
> /* change to existing entry */
> if (strcmp(im->name, ifname) != 0) {
> @@ -114,6 +139,14 @@ int ll_remember_index(struct nlmsghdr *n, void
> *arg)
> hlist_add_head(&im->name_hash, &name_head[h]);
> }
>
> + if (im->alias) {
> + hlist_del(&im->alias_hash);
> + if (ifalias) {
> + h = namehash(ifalias) & (IDXMAP_SIZE -
> 1);
> + hlist_add_head(&im->alias_hash,
> &alias_head[h]);
> + }
> + }
> +
> im->flags = ifi->ifi_flags;
> return 0;
> }
> @@ -132,6 +165,12 @@ int ll_remember_index(struct nlmsghdr *n, void
> *arg)
> h = namehash(ifname) & (IDXMAP_SIZE - 1);
> hlist_add_head(&im->name_hash, &name_head[h]);
>
> + if (ifalias) {
> + im->alias = strdup(ifalias);
> + h = namehash(ifalias) & (IDXMAP_SIZE - 1);
> + hlist_add_head(&im->alias_hash, &alias_head[h]);
> + }
> +
> return 0;
> }
>
> @@ -152,7 +191,7 @@ static unsigned int ll_idx_a2n(const char *name)
> return idx;
> }
>
> -static int ll_link_get(const char *name, int index)
> +static int ll_link_get(const char *name, const char *alias, int
> index)
> {
> struct {
> struct nlmsghdr n;
> @@ -176,6 +215,9 @@ static int ll_link_get(const char *name, int
> index)
> if (name)
> addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name,
> strlen(name) + 1);
> + if (alias)
> + addattr_l(&req.n, sizeof(req), IFLA_IFALIAS, alias,
> + strlen(alias) + 1);
>
> if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n, &answer) < 0)
> goto out;
> @@ -206,7 +248,7 @@ const char *ll_index_to_name(unsigned int idx)
> if (im)
> return im->name;
>
> - if (ll_link_get(NULL, idx) == idx) {
> + if (ll_link_get(NULL, NULL, idx) == idx) {
> im = ll_get_by_index(idx);
> if (im)
> return im->name;
> @@ -252,7 +294,13 @@ unsigned ll_name_to_index(const char *name)
> if (im)
> return im->index;
>
> - idx = ll_link_get(name, 0);
> + im = ll_get_by_alias(name);
> + if (im)
> + return im->index;
> +
> + idx = ll_link_get(name, NULL, 0);
> + if (idx == 0)
> + idx = ll_link_get(NULL, name, 0);
> if (idx == 0)
> idx = if_nametoindex(name);
> if (idx == 0)
> @@ -270,7 +318,10 @@ void ll_drop_by_index(unsigned index)
>
> hlist_del(&im->idx_hash);
> hlist_del(&im->name_hash);
> -
> + if (im->alias) {
> + hlist_del(&im->alias_hash);
> + free(im->alias);
> + }
> free(im);
> }
>
>
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