kernel: does not learn routes with RTPROT_KERNEL

[Maria Matejka]

Hello!

On first sight, this looks good. Gonna do some checks and tests and let 
you know whether anything more is needed from you.

Thank you for your patch!
Maria

On 8/24/23 01:38, Pavel Šorejs via Bird-users wrote:
> Here is first version - based on master
>
>
> Pavel
>
> ---
>  doc/bird.sgml          | 11 ++++++-----
>  sysdep/linux/netlink.c |  2 +-
>  sysdep/unix/krt.Y      |  7 ++++++-
>  sysdep/unix/krt.c      | 15 +++++++++++----
>  sysdep/unix/krt.h      |  4 ++++
>  5 files changed, 28 insertions(+), 11 deletions(-)
>
> diff --git a/doc/bird.sgml b/doc/bird.sgml
> index 29e12b7a..af87d5dc 100644
> --- a/doc/bird.sgml
> +++ b/doc/bird.sgml
> @@ -3454,9 +3454,8 @@ on the <cf/learn/ switch, such routes are either 
> ignored or accepted to our
>  table).
>
>  <p>Note that routes created by OS kernel itself, namely direct routes
> -representing IP subnets of associated interfaces, are not imported 
> even with
> -<cf/learn/ enabled. You can use <ref id="direct" name="Direct 
> protocol"> to
> -generate these direct routes.
> +representing IP subnets of associated interfaces, are imported only with
> +<cf/learn all/ enabled.
>
>  <p>If your OS supports only a single routing table, you can configure 
> only one
>  instance of the Kernel protocol. If it supports multiple tables (in 
> order to
> @@ -3487,10 +3486,12 @@ channels.
>      Time in seconds between two consecutive scans of the kernel routing
>      table.
>
> -    <tag><label id="krt-learn">learn <m/switch/</tag>
> +    <tag><label id="krt-learn">learn [<m/all/]</tag>
>      Enable learning of routes added to the kernel routing tables by 
> other
>      routing daemons or by the system administrator. This is possible 
> only on
> -    systems which support identification of route authorship.
> +    systems which support identification of route authorship. By 
> default, routes
> +    created by kernel (marked as "proto kernel") are not imported. 
> Use <m/all/
> +    option to import these routes.
>
>      <tag><label id="krt-kernel-table">kernel table <m/number/</tag>
>      Select which kernel table should this particular instance of the 
> Kernel
> diff --git a/sysdep/linux/netlink.c b/sysdep/linux/netlink.c
> index 1af78766..29446cab 100644
> --- a/sysdep/linux/netlink.c
> +++ b/sysdep/linux/netlink.c
> @@ -1598,7 +1598,7 @@ nl_parse_route(struct nl_parse_state *s, struct 
> nlmsghdr *h)
>
>      case RTPROT_KERNEL:
>        krt_src = KRT_SRC_KERNEL;
> -      return;
> +      break;
>
>      case RTPROT_BIRD:
>        if (!s->scan)
> diff --git a/sysdep/unix/krt.Y b/sysdep/unix/krt.Y
> index 95b54d65..f3eb1393 100644
> --- a/sysdep/unix/krt.Y
> +++ b/sysdep/unix/krt.Y
> @@ -32,6 +32,7 @@ CF_DECLS
>  CF_KEYWORDS(KERNEL, PERSIST, SCAN, TIME, LEARN, DEVICE, ROUTES, 
> GRACEFUL, RESTART, KRT_SOURCE, KRT_METRIC, MERGE, PATHS)
>  CF_KEYWORDS(INTERFACE, PREFERRED)
>
> +%type <i> kern_learn
>  %type <i> kern_mp_limit
>
>  CF_GRAMMAR
> @@ -48,6 +49,10 @@ kern_proto_start: proto_start KERNEL {
>  kern_proto: kern_proto_start proto_name '{' ;
>  kern_proto: kern_proto kern_item ';' ;
>
> +kern_learn:
> + bool { $$ = $1 ? KRT_LEARN_SOME : KRT_LEARN_NONE; }
> + | ALL { $$ = KRT_LEARN_ALL; }
> +
>  kern_mp_limit:
>     /* empty */ { $$ = KRT_DEFAULT_ECMP_LIMIT; }
>   | LIMIT expr  { $$ = $2; if (($2 <= 0) || ($2 > 255)) 
> cf_error("Merge paths limit must be in range 1-255"); }
> @@ -61,7 +66,7 @@ kern_item:
>        /* Scan time of 0 means scan on startup only */
>        THIS_KRT->scan_time = $3 S_;
>     }
> - | LEARN bool {
> + | LEARN kern_learn {
>        THIS_KRT->learn = $2;
>  #ifndef KRT_ALLOW_LEARN
>        if ($2)
> diff --git a/sysdep/unix/krt.c b/sysdep/unix/krt.c
> index 9f95247f..3288fd0c 100644
> --- a/sysdep/unix/krt.c
> +++ b/sysdep/unix/krt.c
> @@ -638,13 +638,14 @@ krt_got_route(struct krt_proto *p, rte *e, s8 src)
>
>  #ifdef KRT_ALLOW_LEARN
>    switch (src)
> -    {
> -    case KRT_SRC_KERNEL:
> -      goto ignore;
> -
> +    {
>      case KRT_SRC_REDIRECT:
>        goto delete;
>
> +    case KRT_SRC_KERNEL:
> +      if (KRT_CF->learn != KRT_LEARN_ALL)
> +        goto ignore;
> +      // fall through
>      case  KRT_SRC_ALIEN:
>        if (KRT_CF->learn)
>      krt_learn_scan(p, e);
> @@ -780,6 +781,12 @@ krt_got_route_async(struct krt_proto *p, rte *e, 
> int new, s8 src)
>        break;
>
>  #ifdef KRT_ALLOW_LEARN
> +  case KRT_SRC_KERNEL:
> +      if (KRT_CF->learn == KRT_LEARN_ALL)
> +    {
> +      krt_learn_async(p, e, new);
> +    }
> +  break;
>      case KRT_SRC_ALIEN:
>        if (KRT_CF->learn)
>      {
> diff --git a/sysdep/unix/krt.h b/sysdep/unix/krt.h
> index 18a206e6..694ebd34 100644
> --- a/sysdep/unix/krt.h
> +++ b/sysdep/unix/krt.h
> @@ -27,6 +27,10 @@ struct kif_proto;
>  #define KRT_REF_SEEN    0x1    /* Seen in table */
>  #define KRT_REF_BEST    0x2    /* Best in table */
>
> +#define KRT_LEARN_NONE 0 /* Don't learn */
> +#define KRT_LEARN_SOME 1 /* Learn some routes (excluding 
> RTPROT_KERNEL) */
> +#define KRT_LEARN_ALL 2 /* Learn all routes */
> +
>  /* Whenever we recognize our own routes, we allow learing of foreign 
> routes */
>
>  #ifdef CONFIG_SELF_CONSCIOUS

-- 
Maria Matejka (she/her) | BIRD Team Leader | CZ.NIC, z.s.p.o.
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