On Wed, Dec 27, 2023 at 09:54:14AM +0100, Otto Moerbeek wrote:
> On Mon, Dec 18, 2023 at 04:42:09PM +0000, Guilherme Janczak wrote:
> 
> > On Mon, Dec 18, 2023 at 07:31:37AM +0100, Otto Moerbeek wrote:
> > > On Sun, Dec 17, 2023 at 05:37:50PM +0100, Otto Moerbeek wrote:
> > >
> > > > On Fri, Dec 15, 2023 at 02:54:19PM +0100, Otto Moerbeek wrote:
> > > >
> > > > > On Sun, Dec 10, 2023 at 09:57:08AM +0100, Otto Moerbeek wrote:
> > > > >
> > > > > > On Fri, Dec 01, 2023 at 09:18:32PM +0000, 
> > > > > > guilherme.janc...@yandex.com wrote:
> > > > > >
> > > > > > > >Synopsis:        Repeated NTP peers in OpenNTPD
> > > > > > > >Category:        user
> > > > > > > >Environment:
> > > > > > >   System      : OpenBSD 7.4
> > > > > > >   Details     : OpenBSD 7.4 (GENERIC.MP) #0: Sun Oct 22 12:13:42 
> > > > > > > MDT 2023
> > > > > > >                    
> > > > > > > r...@syspatch-74-amd64.openbsd.org:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> > > > > > >
> > > > > > >   Architecture: OpenBSD.amd64
> > > > > > >   Machine     : amd64
> > > > > > > >Description:
> > > > > > >   If the same address/domain is specified multiple times in
> > > > > > >   OpenNTPD's configuration file, or if multiple domains resolve
> > > > > > >   to the same IP address, OpenNTPD will treat the same IP address
> > > > > > >   as if it was multiple peers.
> > > > > > > >How-To-Repeat:
> > > > > > >   This can be tested by appending `server 127.0.0.1` multiple
> > > > > > >   times to the configuration file.
> > > > > > >
> > > > > > >   Alternatively, assuming a default OpenNTPD configuration file
> > > > > > >   from OpenBSD 7.4, the following entries can be added to
> > > > > > >   /etc/hosts:
> > > > > > >   127.0.0.1       time.cloudflare.com
> > > > > > >   127.0.0.1       pool.ntp.org
> > > > > > >
> > > > > > >   I noticed this bug using the default 7.4 configuration file. It
> > > > > > >   can happen because time.cloudflare.com is part of pool.ntp.org:
> > > > > > >   https://www.ntppool.org/scores/162.159.200.1
> > > > > > >   https://www.ntppool.org/scores/162.159.200.123
> > > > > > > >Fix:
> > > > > > >   Removing the `server time.cloudflare.com` line from the
> > > > > > >   configuration file is a simple fix the user can make, but
> > > > > > >   OpenNTPD should check if an IP address it tries to add to the
> > > > > > >   list of peers is already a peer, and ignore it if so. If a
> > > > > > >   server is added with the `server` (not `servers`) keyword in the
> > > > > > >   configuration file, OpenNTPD should try the next IP the domain
> > > > > > >   resolves to if applicable.
> > > > > > >
> > > > > >
> > > > > > Thanks for the report, I'll take a look.
> > > > > >
> > > > > >     -Otto
> > > > > >
> > > > >
> > > > > Due to verious reasons this is all a bit complicated, I did not find a
> > > > > nice solution yet. Some patience required.
> > > > >
> > > > >       -Otto
> > > > >
> > > >
> > > > Found some more time. Try this. The approach is: we assume the
> > > > addresses of a pool (from the "servers" keyword) vary over time. So if
> > > > one of the pool addresses is in the address list of a peer ("server")
> > > > we skip it ad try to re-resolve the pool, lookin for a new address, as
> > > > we already did earlier when a pool member doe snot respond.
> > > >
> > > > I decided to not implement "the move to abother address of the list"
> > > > in the "server" case. The address logic is already complex enough.
> > > >
> > > >         -Otto
> > > >
> > > > Index: client.c
> > > > ===================================================================
> > > > RCS file: /home/cvs/src/usr.sbin/ntpd/client.c,v
> > > > diff -u -p -r1.117 client.c
> > > > --- client.c    24 Mar 2022 07:37:19 -0000      1.117
> > > > +++ client.c    17 Dec 2023 09:13:16 -0000
> > > > @@ -108,6 +108,7 @@ client_nextaddr(struct ntp_peer *p)
> > > >                 return (-1);
> > > >
> > > >         if (p->addr_head.a == NULL) {
> > > > +               log_debug("kicking query for %s",  p->addr_head.name);
> > > >                 priv_dns(IMSG_HOST_DNS, p->addr_head.name, p->id);
> > > >                 p->state = STATE_DNS_INPROGRESS;
> > > >                 return (-1);
> > > > @@ -145,7 +146,15 @@ client_query(struct ntp_peer *p)
> > > >         }
> > > >
> > > >         if (p->state < STATE_DNS_DONE || p->addr == NULL)
> > > > -               return (-1);
> > > > +               return (0);
> > > > +
> > > > +       /* if we're a pool member and a peer has taken our address, 
> > > > signal */
> > > > +       if (p->addr_head.pool != 0 && addr_already_used(&p->addr->ss)) {
> > > > +               log_debug("pool addr %s used by peer, will reresolve 
> > > > pool",
> > > > +                   log_sockaddr((struct sockaddr *)&p->addr->ss));
> > > > +               p->senderrors++;
> > > > +               return (0);
> > > > +       }
> > > >
> > > >         if (p->query.fd == -1) {
> > > >                 struct sockaddr *sa = (struct sockaddr *)&p->addr->ss;
> > > > Index: ntp.c
> > > > ===================================================================
> > > > RCS file: /home/cvs/src/usr.sbin/ntpd/ntp.c,v
> > > > diff -u -p -r1.171 ntp.c
> > > > --- ntp.c       6 Dec 2023 15:51:53 -0000       1.171
> > > > +++ ntp.c       17 Dec 2023 09:13:16 -0000
> > > > @@ -54,8 +54,6 @@ int   ntp_dispatch_imsg(void);
> > > >  int    ntp_dispatch_imsg_dns(void);
> > > >  void   peer_add(struct ntp_peer *);
> > > >  void   peer_remove(struct ntp_peer *);
> > > > -int    inpool(struct sockaddr_storage *,
> > > > -           struct sockaddr_storage[MAX_SERVERS_DNS], size_t);
> > > >
> > > >  void
> > > >  ntp_sighdlr(int sig)
> > > > @@ -524,23 +522,52 @@ ntp_dispatch_imsg(void)
> > > >         return (0);
> > > >  }
> > > >
> > > > -int
> > > > +static int
> > > > +addr_equal(struct sockaddr_storage *a, struct sockaddr_storage *b)
> > > > +{
> > > > +       if (a->ss_family != b->ss_family)
> > > > +               return 0;
> > > > +       if (a->ss_family == AF_INET) {
> > > > +               if (((struct sockaddr_in *)a)->sin_addr.s_addr ==
> > > > +                   ((struct sockaddr_in *)b)->sin_addr.s_addr)
> > > > +                       return 1;
> > > > +       } else if (memcmp(&((struct sockaddr_in6 *)a)->sin6_addr,
> > > > +           &((struct sockaddr_in6 *)b)->sin6_addr,
> > > > +           sizeof(struct sockaddr_in6)) == 0) {
> > > > +               return 1;
> > > > +       }
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static int
> > > >  inpool(struct sockaddr_storage *a,
> > > >      struct sockaddr_storage old[MAX_SERVERS_DNS], size_t n)
> > > >  {
> > > >         size_t i;
> > > >
> > > >         for (i = 0; i < n; i++) {
> > > > -               if (a->ss_family != old[i].ss_family)
> > > > +               if (addr_equal(a, &old[i]))
> > > > +                       return 1;
> > > > +       }
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +/* check to see af an address is already listed by a "server" peer
> > > > +   in that case, it does not get added to a pool */
> > > > +int
> > > > +addr_already_used(struct sockaddr_storage *a)
> > > > +{
> > > > +       struct ntp_peer *peer;
> > > > +       struct ntp_addr *addr;
> > > > +
> > > > +       TAILQ_FOREACH(peer, &conf->ntp_peers, entry) {
> > > > +               if (peer->addr_head.pool != 0)
> > > >                         continue;
> > > > -               if (a->ss_family == AF_INET) {
> > > > -                       if (((struct sockaddr_in *)a)->sin_addr.s_addr 
> > > > ==
> > > > -                           ((struct sockaddr_in 
> > > > *)&old[i])->sin_addr.s_addr)
> > > > +               addr = peer->addr_head.a;
> > > > +               while (addr != NULL) {
> > > > +                       if (addr_equal(a, &addr->ss))
> > > >                                 return 1;
> > > > -               } else if (memcmp(&((struct sockaddr_in6 
> > > > *)a)->sin6_addr,
> > > > -                   &((struct sockaddr_in6 *)&old[i])->sin6_addr,
> > > > -                   sizeof(struct sockaddr_in6)) == 0) {
> > > > -                       return 1;
> > > > +                       addr = addr->next;
> > > >                 }
> > > >         }
> > > >         return 0;
> > > > @@ -628,8 +655,11 @@ ntp_dispatch_imsg_dns(void)
> > > >                                                 free(h);
> > > >                                                 continue;
> > > >                                         }
> > > > -                                       if (inpool(&h->ss, existing,
> > > > -                                           n)) {
> > > > +                                       if (addr_already_used(&h->ss) ||
> > > > +                                           inpool(&h->ss, existing, 
> > > > n)) {
> > > > +                                               log_debug("skipping 
> > > > address %s for %s",
> > > > +                                                   
> > > > log_sockaddr((struct sockaddr *)
> > > > +                                                   &h->ss), 
> > > > peer->addr_head.name);
> > > >                                                 free(h);
> > > >                                                 continue;
> > > >                                         }
> > > > @@ -660,8 +690,11 @@ ntp_dispatch_imsg_dns(void)
> > > >                         }
> > > >                         if (dlen != 0)
> > > >                                 fatalx("IMSG_HOST_DNS: dlen != 0");
> > > > -                       if (peer->addr_head.pool)
> > > > -                               peer_remove(peer);
> > > > +                       if (peer->addr_head.pool) {
> > > > +                               if (peercount > addrcount)
> > > > +                                       peer_remove(peer);
> > > > +                               peer->state = STATE_NONE;
> > > > +                       }
> > > >                         else
> > > >                                 client_addr_init(peer);
> > > >                         break;
> > > > Index: ntpd.h
> > > > ===================================================================
> > > > RCS file: /home/cvs/src/usr.sbin/ntpd/ntpd.h,v
> > > > diff -u -p -r1.152 ntpd.h
> > > > --- ntpd.h      27 Nov 2022 13:19:00 -0000      1.152
> > > > +++ ntpd.h      17 Dec 2023 09:13:16 -0000
> > > > @@ -371,6 +371,7 @@ int server_dispatch(int, struct ntpd_con
> > > >  int    client_peer_init(struct ntp_peer *);
> > > >  int    client_addr_init(struct ntp_peer *);
> > > >  int    client_nextaddr(struct ntp_peer *);
> > > > +int    addr_already_used(struct sockaddr_storage *);
> > > >  int    client_query(struct ntp_peer *);
> > > >  int    client_dispatch(struct ntp_peer *, u_int8_t, u_int8_t);
> > > >  void   client_log_error(struct ntp_peer *, const char *, int);
> > > >
> > >
> > > Previous diff had a write after free.
> > >
> > >   -Otto
> > >
> > > Index: client.c
> > > ===================================================================
> > > RCS file: /home/cvs/src/usr.sbin/ntpd/client.c,v
> > > diff -u -p -r1.117 client.c
> > > --- client.c      24 Mar 2022 07:37:19 -0000      1.117
> > > +++ client.c      18 Dec 2023 06:20:13 -0000
> > > @@ -108,6 +108,7 @@ client_nextaddr(struct ntp_peer *p)
> > >           return (-1);
> > >
> > >   if (p->addr_head.a == NULL) {
> > > +         log_debug("kicking query for %s",  p->addr_head.name);
> > >           priv_dns(IMSG_HOST_DNS, p->addr_head.name, p->id);
> > >           p->state = STATE_DNS_INPROGRESS;
> > >           return (-1);
> > > @@ -145,7 +146,15 @@ client_query(struct ntp_peer *p)
> > >   }
> > >
> > >   if (p->state < STATE_DNS_DONE || p->addr == NULL)
> > > -         return (-1);
> > > +         return (0);
> > > +
> > > + /* if we're a pool member and a peer has taken our address, signal */
> > > + if (p->addr_head.pool != 0 && addr_already_used(&p->addr->ss)) {
> > > +         log_debug("pool addr %s used by peer, will reresolve pool",
> > > +             log_sockaddr((struct sockaddr *)&p->addr->ss));
> > > +         p->senderrors++;
> > > +         return (0);
> > > + }
> > >
> > >   if (p->query.fd == -1) {
> > >           struct sockaddr *sa = (struct sockaddr *)&p->addr->ss;
> > > Index: ntp.c
> > > ===================================================================
> > > RCS file: /home/cvs/src/usr.sbin/ntpd/ntp.c,v
> > > diff -u -p -r1.171 ntp.c
> > > --- ntp.c 6 Dec 2023 15:51:53 -0000       1.171
> > > +++ ntp.c 18 Dec 2023 06:20:13 -0000
> > > @@ -54,8 +54,6 @@ int     ntp_dispatch_imsg(void);
> > >  int      ntp_dispatch_imsg_dns(void);
> > >  void     peer_add(struct ntp_peer *);
> > >  void     peer_remove(struct ntp_peer *);
> > > -int      inpool(struct sockaddr_storage *,
> > > -     struct sockaddr_storage[MAX_SERVERS_DNS], size_t);
> > >
> > >  void
> > >  ntp_sighdlr(int sig)
> > > @@ -524,23 +522,52 @@ ntp_dispatch_imsg(void)
> > >   return (0);
> > >  }
> > >
> > > -int
> > > +static int
> > > +addr_equal(struct sockaddr_storage *a, struct sockaddr_storage *b)
> > > +{
> > > + if (a->ss_family != b->ss_family)
> > > +         return 0;
> > > + if (a->ss_family == AF_INET) {
> > > +         if (((struct sockaddr_in *)a)->sin_addr.s_addr ==
> > > +             ((struct sockaddr_in *)b)->sin_addr.s_addr)
> > > +                 return 1;
> > > + } else if (memcmp(&((struct sockaddr_in6 *)a)->sin6_addr,
> > > +     &((struct sockaddr_in6 *)b)->sin6_addr,
> > > +     sizeof(struct sockaddr_in6)) == 0) {
> > > +         return 1;
> > > + }
> > > + return 0;
> > > +}
> > > +
> > > +static int
> > >  inpool(struct sockaddr_storage *a,
> > >      struct sockaddr_storage old[MAX_SERVERS_DNS], size_t n)
> > >  {
> > >   size_t i;
> > >
> > >   for (i = 0; i < n; i++) {
> > > -         if (a->ss_family != old[i].ss_family)
> > > +         if (addr_equal(a, &old[i]))
> > > +                 return 1;
> > > + }
> > > + return 0;
> > > +}
> > > +
> > > +/* check to see af an address is already listed by a "server" peer
> > > +   in that case, it does not get added to a pool */
> > > +int
> > > +addr_already_used(struct sockaddr_storage *a)
> > > +{
> > > + struct ntp_peer *peer;
> > > + struct ntp_addr *addr;
> > > +
> > > + TAILQ_FOREACH(peer, &conf->ntp_peers, entry) {
> > > +         if (peer->addr_head.pool != 0)
> > >                   continue;
> > > -         if (a->ss_family == AF_INET) {
> > > -                 if (((struct sockaddr_in *)a)->sin_addr.s_addr ==
> > > -                     ((struct sockaddr_in *)&old[i])->sin_addr.s_addr)
> > > +         addr = peer->addr_head.a;
> > > +         while (addr != NULL) {
> > > +                 if (addr_equal(a, &addr->ss))
> > >                           return 1;
> > > -         } else if (memcmp(&((struct sockaddr_in6 *)a)->sin6_addr,
> > > -             &((struct sockaddr_in6 *)&old[i])->sin6_addr,
> > > -             sizeof(struct sockaddr_in6)) == 0) {
> > > -                 return 1;
> > > +                 addr = addr->next;
> > >           }
> > >   }
> > >   return 0;
> > > @@ -628,8 +655,11 @@ ntp_dispatch_imsg_dns(void)
> > >                                           free(h);
> > >                                           continue;
> > >                                   }
> > > -                                 if (inpool(&h->ss, existing,
> > > -                                     n)) {
> > > +                                 if (addr_already_used(&h->ss) ||
> > > +                                     inpool(&h->ss, existing, n)) {
> > > +                                         log_debug("skipping address %s 
> > > for %s",
> > > +                                             log_sockaddr((struct 
> > > sockaddr *)
> > > +                                             &h->ss), 
> > > peer->addr_head.name);
> > >                                           free(h);
> > >                                           continue;
> > >                                   }
> > > @@ -660,8 +690,12 @@ ntp_dispatch_imsg_dns(void)
> > >                   }
> > >                   if (dlen != 0)
> > >                           fatalx("IMSG_HOST_DNS: dlen != 0");
> > > -                 if (peer->addr_head.pool)
> > > -                         peer_remove(peer);
> > > +                 if (peer->addr_head.pool) {
> > > +                         if (peercount > addrcount)
> > > +                                 peer_remove(peer);
> > > +                         else
> > > +                                 peer->state = STATE_NONE;
> > > +                 }
> > >                   else
> > >                           client_addr_init(peer);
> > >                   break;
> > > Index: ntpd.h
> > > ===================================================================
> > > RCS file: /home/cvs/src/usr.sbin/ntpd/ntpd.h,v
> > > diff -u -p -r1.152 ntpd.h
> > > --- ntpd.h        27 Nov 2022 13:19:00 -0000      1.152
> > > +++ ntpd.h        18 Dec 2023 06:20:13 -0000
> > > @@ -371,6 +371,7 @@ int   server_dispatch(int, struct ntpd_con
> > >  int      client_peer_init(struct ntp_peer *);
> > >  int      client_addr_init(struct ntp_peer *);
> > >  int      client_nextaddr(struct ntp_peer *);
> > > +int      addr_already_used(struct sockaddr_storage *);
> > >  int      client_query(struct ntp_peer *);
> > >  int      client_dispatch(struct ntp_peer *, u_int8_t, u_int8_t);
> > >  void     client_log_error(struct ntp_peer *, const char *, int);
> > >
> > 
> > That solves the bug with the default config file. I can see how a
> > repeated peer is marked as "not resolved," and how ntpd tries to find a
> > new unique IP every poll interval, but as you mentioned, it only checks
> > if a pool address matches a peer address.
> > 
> > Testing with this config file:
> > ```
> > servers br.pool.ntp.org
> > servers time.cloudflare.com
> > 
> > constraint from "9.9.9.9"              # quad9 v4 without DNS
> > constraint from "2620:fe::fe"          # quad9 v6 without DNS
> > constraints from "www.google.com"      # intentionally not 8.8.8.8
> > ```
> > 
> > I still see repeated peers (162.159.200.1 and 162.159.200.123):
> > ```
> > $ ntpctl -s all
> > 8/8 peers valid, constraint offset -2s, clock unsynced
> > 
> > peer
> >    wt tl st  next  poll          offset       delay      jitter
> > 162.159.200.1 from pool br.pool.ntp.org
> >     1 10  3   28s   33s         0.147ms     9.531ms     0.246ms
> > 168.181.125.82 from pool br.pool.ntp.org
> >     1 10  2   27s   34s        11.375ms    38.489ms     0.436ms
> > 162.159.200.123 from pool br.pool.ntp.org
> >     1 10  3    6s   34s        -0.585ms    11.994ms     0.351ms
> > 138.99.160.244 from pool br.pool.ntp.org
> >     1 10  3    1s   32s         1.017ms    18.735ms     1.252ms
> > 2606:4700:f1::123 from pool time.cloudflare.com
> >     1 10  3   30s   34s         1.029ms    14.623ms     3.945ms
> > 2606:4700:f1::1 from pool time.cloudflare.com
> >     1 10  3   30s   33s        -0.617ms    11.538ms     0.381ms
> > 162.159.200.1 from pool time.cloudflare.com
> >     1 10  3    2s   32s        -1.867ms    21.497ms     6.333ms
> > 162.159.200.123 from pool time.cloudflare.com
> >     1 10  3    5s   32s         2.403ms    14.003ms     6.336ms
> > ```
> > 
> > Trying multiple pool.ntp.org regions helps find one currently serving a
> > time.cloudflare.com address.
> > 
> > Also, I can't seem to get the debug messages. They don't show up with
> > `ntpd -v` or and `ntpd -dv`.
> > 
> 
> New version that fixes most (though not all) cases.
> 
> The case that is not solved is: if there is overlap in addresses, a
> fixed pool may never be able to use a slot, as another pool may
> "squat" that address. The pool with fixed addresses will then not be
> able to use that address. I think that's acceptable.
> 
>       -Otto
> 
> Index: client.c
> ===================================================================
> RCS file: /home/cvs/src/usr.sbin/ntpd/client.c,v
> diff -u -p -r1.118 client.c
> --- client.c  20 Dec 2023 15:36:36 -0000      1.118
> +++ client.c  26 Dec 2023 17:09:06 -0000
> @@ -108,6 +108,7 @@ client_nextaddr(struct ntp_peer *p)
>               return (-1);
>  
>       if (p->addr_head.a == NULL) {
> +             log_debug("kicking query for %s",  p->addr_head.name);
>               priv_dns(IMSG_HOST_DNS, p->addr_head.name, p->id);
>               p->state = STATE_DNS_INPROGRESS;
>               return (-1);
> @@ -145,7 +146,15 @@ client_query(struct ntp_peer *p)
>       }
>  
>       if (p->state < STATE_DNS_DONE || p->addr == NULL)
> -             return (-1);
> +             return (0);
> +
> +     /* if we're a pool member and a peer has taken our address, signal */
> +     if (p->addr_head.pool != 0 && addr_already_used(&p->addr->ss, 
> p->addr_head.pool)) {
> +             log_debug("pool addr %s used by peer, will reresolve pool",
> +                 log_sockaddr((struct sockaddr *)&p->addr->ss));
> +             p->senderrors++;
> +             return (0);
> +     }
>  
>       if (p->query.fd == -1) {
>               struct sockaddr *sa = (struct sockaddr *)&p->addr->ss;
> Index: ntp.c
> ===================================================================
> RCS file: /home/cvs/src/usr.sbin/ntpd/ntp.c,v
> diff -u -p -r1.172 ntp.c
> --- ntp.c     20 Dec 2023 15:36:36 -0000      1.172
> +++ ntp.c     26 Dec 2023 17:09:06 -0000
> @@ -54,8 +54,6 @@ int ntp_dispatch_imsg(void);
>  int  ntp_dispatch_imsg_dns(void);
>  void peer_add(struct ntp_peer *);
>  void peer_remove(struct ntp_peer *);
> -int  inpool(struct sockaddr_storage *,
> -         struct sockaddr_storage[MAX_SERVERS_DNS], size_t);
>  
>  void
>  ntp_sighdlr(int sig)
> @@ -519,23 +517,52 @@ ntp_dispatch_imsg(void)
>       return (0);
>  }
>  
> -int
> +static int
> +addr_equal(struct sockaddr_storage *a, struct sockaddr_storage *b)
> +{
> +     if (a->ss_family != b->ss_family)
> +             return 0;
> +     if (a->ss_family == AF_INET) {
> +             if (((struct sockaddr_in *)a)->sin_addr.s_addr ==
> +                 ((struct sockaddr_in *)b)->sin_addr.s_addr)
> +                     return 1;
> +     } else if (memcmp(&((struct sockaddr_in6 *)a)->sin6_addr,
> +         &((struct sockaddr_in6 *)b)->sin6_addr,
> +         sizeof(struct sockaddr_in6)) == 0) {
> +             return 1;
> +     }
> +     return 0;
> +}
> +
> +static int
>  inpool(struct sockaddr_storage *a,
>      struct sockaddr_storage old[MAX_SERVERS_DNS], size_t n)
>  {
>       size_t i;
>  
>       for (i = 0; i < n; i++) {
> -             if (a->ss_family != old[i].ss_family)
> +             if (addr_equal(a, &old[i]))
> +                     return 1;
> +     }
> +     return 0;
> +}
> +
> +/* check to see af an address is already listed
> +   in that case, it does not get added to a pool */
> +int
> +addr_already_used(struct sockaddr_storage *a, int skippool)
> +{
> +     struct ntp_peer *peer;
> +     struct ntp_addr *addr;
> +
> +     TAILQ_FOREACH(peer, &conf->ntp_peers, entry) {
> +             if (peer->addr_head.pool == skippool)
>                       continue;
> -             if (a->ss_family == AF_INET) {
> -                     if (((struct sockaddr_in *)a)->sin_addr.s_addr ==
> -                         ((struct sockaddr_in *)&old[i])->sin_addr.s_addr)
> +             addr = peer->addr_head.a;
> +             while (addr != NULL) {
> +                     if (addr_equal(a, &addr->ss))
>                               return 1;
> -             } else if (memcmp(&((struct sockaddr_in6 *)a)->sin6_addr,
> -                 &((struct sockaddr_in6 *)&old[i])->sin6_addr,
> -                 sizeof(struct sockaddr_in6)) == 0) {
> -                     return 1;
> +                     addr = addr->next;
>               }
>       }
>       return 0;
> @@ -623,8 +650,11 @@ ntp_dispatch_imsg_dns(void)
>                                               free(h);
>                                               continue;
>                                       }
> -                                     if (inpool(&h->ss, existing,
> -                                         n)) {
> +                                     if (addr_already_used(&h->ss, 
> peer->addr_head.pool) ||
> +                                         inpool(&h->ss, existing, n)) {
> +                                             log_debug("skipping address %s 
> for %s",
> +                                                 log_sockaddr((struct 
> sockaddr *)
> +                                                 &h->ss), 
> peer->addr_head.name);
>                                               free(h);
>                                               continue;
>                                       }
> @@ -654,8 +684,12 @@ ntp_dispatch_imsg_dns(void)
>                       }
>                       if (dlen != 0)
>                               fatalx("IMSG_HOST_DNS: dlen != 0");
> -                     if (peer->addr_head.pool)
> -                             peer_remove(peer);
> +                     if (peer->addr_head.pool) {
> +                             if (peercount > addrcount)
> +                                     peer_remove(peer);
> +                             else
> +                                     peer->state = STATE_NONE;
> +                     }
>                       else
>                               client_addr_init(peer);
>                       break;
> Index: ntpd.h
> ===================================================================
> RCS file: /home/cvs/src/usr.sbin/ntpd/ntpd.h,v
> diff -u -p -r1.153 ntpd.h
> --- ntpd.h    20 Dec 2023 15:36:36 -0000      1.153
> +++ ntpd.h    26 Dec 2023 17:09:06 -0000
> @@ -371,6 +371,7 @@ int       server_dispatch(int, struct ntpd_con
>  int  client_peer_init(struct ntp_peer *);
>  int  client_addr_init(struct ntp_peer *);
>  int  client_nextaddr(struct ntp_peer *);
> +int  addr_already_used(struct sockaddr_storage *, int);
>  int  client_query(struct ntp_peer *);
>  int  client_dispatch(struct ntp_peer *, u_int8_t, u_int8_t);
>  void client_log_error(struct ntp_peer *, const char *, int);
> 


With 2 `server` that resolve to the same IP, I still get repeated peers.

Config file:
```
server br.pool.ntp.org
server time.cloudflare.com
```

jan-z87-obsd# ntpd -dvv
ntp engine ready
kicking query for br.pool.ntp.org
kicking query for time.cloudflare.com
Reset constraint info
trying to resolve br.pool.ntp.org
resolve br.pool.ntp.org done: 4
trying to resolve time.cloudflare.com
resolve time.cloudflare.com done: 4
reply from 162.159.200.123: offset 0.004251 delay 0.018725, next query 5s
reply from 162.159.200.123: offset 0.004367 delay 0.019038, next query 8s
reply from 162.159.200.123: offset 0.000310 delay 0.010170, next query 8s
reply from 162.159.200.123: offset 0.000472 delay 0.010892, next query 8s
reply from 162.159.200.123: offset 0.000274 delay 0.009892, next query 6s
reply from 162.159.200.123: offset 0.000536 delay 0.010931, next query 6s
peer 162.159.200.123 now valid
reply from 162.159.200.123: offset 0.000302 delay 0.009911, next query 9s
peer 162.159.200.123 now valid
reply from 162.159.200.123: offset 0.000538 delay 0.010939, next query 7s
reply from 162.159.200.123: offset 0.000601 delay 0.010461, next query 6s
reply from 162.159.200.123: offset 0.000588 delay 0.010966, next query 5s


$ ntpctl -s all
2/2 peers valid, clock unsynced

peer
   wt tl st  next  poll          offset       delay      jitter
162.159.200.123 br.pool.ntp.org
    1  8  3   16s   31s         1.143ms    12.211ms     3.838ms
162.159.200.123 time.cloudflare.com
    1  8  3   17s   31s         1.015ms    11.525ms     3.961ms


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