[OpenWrt-Devel] [PATCH] [odhcp6c] ra: clear RA information and request new after link-up event or SIGUSR2

[Hans Dedecker]

Hi,

On Mon, Mar 18, 2019 at 8:51 PM Pavel Merzlyakov
<pavel.merzlyakov at gmail.com> wrote:
>
> Hi,
>
> >Can you be elaborate more in detail what use case you want to cover
> >with this patch; in other words what is not working now ?
> Ok,
> my setup:
> Two peer routers A and B which both connected to gateway C.
> Routers A and B have public IPv6 addresses on WAN interfaces from same subnet (because of RA on C) and private IPv6 addresses on LAN interfaces.
> and issue:
> If I unplug router B from C and then plug it in LAN port of router A:
> 1) Router B does not send Router Solicitation message. So router B does not have a valid gateway for some time.
Since we've linksensing support in netifd the wan/wan6 interface
should be brought down when the cable is unplugged; the wan/wan6
interface will be brought up again when the cable is plugged in. This
means odhcp6c will be restarted and will start sending RS; why is this
not the case in your setup ?

Hans
> 2) Router B does not delete old IPv6 address on the WAN. After first Router Advertisement message router B is capable to send a request via new gateway A, but it can't receive responses because of invalid/old source address in request.
>
>
> >Why do you want to restart RA if an SIGUSR2 signal is received ?
> Because I assume that SIGUSR2 signal is equivalent to link-up event  (see odhcp6c:674 -> https://git.openwrt.org/?p=project/odhcp6c.git;a=blob;f=src/odhcp6c.c;h=19a86f2654bf3c59b0f47cf0aedd87235187bf89;hb=d2e247d8d87ecf8c60fcf0acdad05667bd379521#l674).
> In my case I use hotplug script witch on link-up sends SIGUSR2 signal to odhcp6c (it's connected to bridge interface).
> ra_restart () could be called without condition in beginning of the main loop.
>
> Br,
> Pavel
>
> On Mon, 18 Mar 2019 at 18:26, Hans Dedecker <dedeckeh at gmail.com> wrote:
>>
>> Hi,
>>
>> On Mon, Mar 18, 2019 at 2:43 PM <pavel.merzlyakov at gmail.com> wrote:
>> >
>> > From: Pavel Merzlyakov <pavel.merzlyakov at gmail.com>
>> >
>> > A subnet may be changed after link-up event
>> Can you be elaborate more in detail what use case you want to cover
>> with this patch; in other words what is not working now ?
>> >
>> > Signed-off-by: Pavel Merzlyakov <pavel.merzlyakov at gmail.com>
>> > ---
>> >  src/odhcp6c.c |  3 +++
>> >  src/ra.c      | 20 +++++++++++++++++---
>> >  src/ra.h      |  1 +
>> >  3 files changed, 21 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/src/odhcp6c.c b/src/odhcp6c.c
>> > index 19a86f2..dd20f39 100644
>> > --- a/src/odhcp6c.c
>> > +++ b/src/odhcp6c.c
>> > @@ -455,6 +455,9 @@ int main(_unused int argc, char* const argv[])
>> >
>> >                 syslog(LOG_NOTICE, "(re)starting transaction on %s", ifname);
>> >
>> > +               if (signal_usr2)
>> > +                       ra_restart();
>> Why do you want to restart RA if an SIGUSR2 signal is received ?
>>
>> Hans
>> > +
>> >                 signal_usr1 = signal_usr2 = false;
>> >                 int mode = dhcpv6_set_ia_mode(ia_na_mode, ia_pd_mode);
>> >                 if (mode != DHCPV6_STATELESS)
>> > diff --git a/src/ra.c b/src/ra.c
>> > index 898f449..917df11 100644
>> > --- a/src/ra.c
>> > +++ b/src/ra.c
>> > @@ -55,6 +55,7 @@ static int sock = -1, rtnl = -1;
>> >  static int if_index = 0;
>> >  static char if_name[IF_NAMESIZE] = {0};
>> >  static volatile int rs_attempt = 0;
>> > +static const int rs_attempt_limit = 4;
>> >  static struct in6_addr lladdr = IN6ADDR_ANY_INIT;
>> >  static unsigned int ra_options = 0;
>> >  static unsigned int ra_holdoff_interval = 0;
>> > @@ -179,6 +180,20 @@ failure:
>> >         return -1;
>> >  }
>> >
>> > +void ra_restart(void)
>> > +{
>> > +       const int rs_attempt_old = rs_attempt;
>> > +
>> > +       odhcp6c_clear_state(STATE_RA_PREFIX);
>> > +       odhcp6c_clear_state(STATE_RA_ROUTE);
>> > +       odhcp6c_clear_state(STATE_RA_DNS);
>> > +       odhcp6c_clear_state(STATE_RA_SEARCH);
>> > +
>> > +       rs_attempt = 0;
>> > +       if (rs_attempt_old == 0 || rs_attempt_old >= rs_attempt_limit)
>> > +               ra_send_rs(SIGALRM);
>> > +}
>> > +
>> >  static void ra_send_rs(int signal __attribute__((unused)))
>> >  {
>> >         const struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_ROUTERS, if_index};
>> > @@ -193,7 +208,7 @@ static void ra_send_rs(int signal __attribute__((unused)))
>> >         if (sendto(sock, &rs, len, MSG_DONTWAIT, (struct sockaddr*)&dest, sizeof(dest)) < 0)
>> >                 syslog(LOG_ERR, "Failed to send RS (%s)",  strerror(errno));
>> >
>> > -       if (++rs_attempt <= 3)
>> > +       if (++rs_attempt < rs_attempt_limit)
>> >                 alarm(4);
>> >  }
>> >
>> > @@ -243,8 +258,7 @@ bool ra_link_up(void)
>> >         if (ret) {
>> >                 syslog(LOG_NOTICE, "carrier => %i event on %s", (int)!nocarrier, if_name);
>> >
>> > -               rs_attempt = 0;
>> > -               ra_send_rs(SIGALRM);
>> > +               ra_restart();
>> >         }
>> >
>> >         return ret;
>> > diff --git a/src/ra.h b/src/ra.h
>> > index 9acc8cd..4ec208f 100644
>> > --- a/src/ra.h
>> > +++ b/src/ra.h
>> > @@ -46,5 +46,6 @@ struct icmpv6_opt_route_info {
>> >
>> >  int ra_init(const char *ifname, const struct in6_addr *ifid,
>> >                 unsigned int options, unsigned int holdoff_interval);
>> > +void ra_restart(void);
>> >  bool ra_link_up(void);
>> >  bool ra_process(void);
>> > --
>> > 2.21.0
>> >
>> >
>> > _______________________________________________
>> > openwrt-devel mailing list
>> > openwrt-devel at lists.openwrt.org
>> > https://lists.openwrt.org/mailman/listinfo/openwrt-devel

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