On Tue, Nov 26, 2024 at 05:39:39AM +0100, Stefano Brivio wrote: > On Tue, 26 Nov 2024 15:01:06 +1100 > David Gibson wrote: > > > On Mon, Nov 25, 2024 at 12:50:37AM +0100, Stefano Brivio wrote: > > > There are setups where no host interface is available or configured > > > at all, intentionally or not, temporarily or not, but users expect > > > (Podman) containers to run in any case as they did with slirp4netns, > > > and we're now getting reports that we broke such setups at a rather > > > alarming rate. > > > > This looks pretty good to me. It's simpler than I feared, and I don't > > think it will tie our hands much in terms of future fancier handling > > (netlink monitors, no-template-interface mode etc.). I'm pretty good > > to go ahead with this soon. > > > > I do have a few thoughts on some details which might be polished, see > > below. > > > > > To this end, if we don't find any usable host interface, instead of > > > exiting: > > > > > > - for IPv4, use 169.254.2.1 as guest/container address and 169.254.2.2 > > > as default gateway > > > > > > - for IPv6, don't assign any address (forcibly disable DHCPv6), and > > > use the *first* link-local address we observe to represent the > > > guest/container. Advertise fe80::1 as default gateway > > > > > > - use 'tap0' as default interface name for pasta > > > > > > Change ifi4 and ifi6 in struct ctx to int and accept a special -1 > > > value meaning that no host interface was selected, but the IP family > > > is enabled. The fact that the kernel uses unsigned int values for > > > those is not an issue as 1. one can't create so many interfaces > > > anyway and 2. we otherwise handle those values transparently. > > > > ifi4 and ifi6 are currently kind of overloaded. A few places that > > actually need to deal with the host side plumbing use them for the > > interface index. Most places use these only to tell if IPv4/IPv6 is > > enabled (for the guest). > > > > This patch is disconnecting whether we have IPv4/IPv6 enabled from > > whether there exists a suitable external interface. So, I think it > > makes sense to disconnect the variables as well, rather than > > complexifying the encoding into ifi4/ifi6. > > > > I'd suggest instead that we introduce new boolean ip[46]_enabled > > variables, and change all the places that check ifi4/ifi6 only for > > that reason to use those instead. That can be a preiminary patch. > > Then we keep the encoding of ifi4/ifi6 as is. > > That turns this patch into a series, which is exactly what I'm trying > to avoid, for no particular advantage. As you say below: "slightly > cleaner". > > I think we should be responsible toward distribution maintainers > (including myself) who might be trying to fix a pressing issue with a > _simple_ backport. Ah, yeah, I forgot about the complexity it would add for backporting. Ok fair enough, we can fix this up later. > > I think that will make things slightly cleaner and not a great deal > > harder for this initial version of a "local" setting. It will also > > extend more naturally if we have future modes that can interact with > > multiple host side interfaces or other more complex scenarios. > > That can be changed later as needed. > > > > Fix a botched conditional in conf_print() to actually skip printing > > > DHCPv6 information if DHCPv6 is disabled (and skip printing NDP > > > information if NDP is disabled). > > > > > > Link: https://github.com/containers/podman/issues/24614 > > > Signed-off-by: Stefano Brivio > > > --- > > > v2: > > > - drop fixed link-local address for IPv6 > > > - change addresses to be reminiscent of libslirp's default choices > > > - add man page changes and commit message > > > - fix several things around, from testing (checked with several > > > --map-guest-addr and --map-host-loopback combinations etc.) > > > > > > conf.c | 92 +++++++++++++++++++++++++++++++++++++++++++++------------ > > > passt.1 | 33 +++++++++++++++++---- > > > passt.h | 8 ++--- > > > pasta.c | 7 +++-- > > > tap.c | 3 ++ > > > 5 files changed, 113 insertions(+), 30 deletions(-) > > > > > > diff --git a/conf.c b/conf.c > > > index 86566db..551c2b0 100644 > > > --- a/conf.c > > > +++ b/conf.c > > > @@ -48,6 +48,20 @@ > > > > > > #define NETNS_RUN_DIR "/run/netns" > > > > > > +#define IP4_LL_GUEST_ADDR (struct in_addr){ htonl_constant(0xa9fe0201) } > > > + /* 169.254.2.1, libslirp default: 10.0.2.1 */ > > > + > > > +#define IP4_LL_GUEST_GW (struct in_addr){ htonl_constant(0xa9fe0202) } > > > + /* 169.254.2.2, libslirp default: 10.0.2.2 */ > > > + > > > +#define IP4_LL_PREFIX_LEN 16 > > > + > > > +#define IP6_LL_GUEST_GW (struct in6_addr) \ > > > + {{{ 0xfe, 0x80, 0, 0, 0, 0, 0, 0, \ > > > + 0, 0, 0, 0, 0, 0, 0, 0x01 }}} > > > + > > > +const char *pasta_default_ifn = "tap0"; > > > > Not sure I like this as a default name, though I guess it's fine. It > > kind of exposes the underlying mechanisms we're using in a way that's > > not really necessary. Maybe just call it "pasta" or "pasta0"? > > That's the default in slirp4netns, and if we have a slight chance of > being slightly more compatible, I'd pick that over proving a point or > being correct. Ok, that seems a good enough reason for "tap0". > > > + > > > /** > > > * next_chunk - Return the next piece of a string delimited by a character > > > * @s: String to search > > > @@ -631,7 +645,7 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4) > > > ifi = nl_get_ext_if(nl_sock, AF_INET); > > > > > > if (!ifi) { > > > - info("Couldn't pick external interface: disabling IPv4"); > > > + debug("Failed to detect external interface for IPv4"); > > > return 0; > > > } > > > > > > @@ -639,8 +653,8 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4) > > > int rc = nl_route_get_def(nl_sock, ifi, AF_INET, > > > &ip4->guest_gw); > > > if (rc < 0) { > > > - err("Couldn't discover IPv4 gateway address: %s", > > > - strerror(-rc)); > > > + debug("Couldn't discover IPv4 gateway address: %s", > > > + strerror(-rc)); > > > return 0; > > > } > > > } > > > @@ -649,8 +663,8 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4) > > > int rc = nl_addr_get(nl_sock, ifi, AF_INET, > > > &ip4->addr, &ip4->prefix_len, NULL); > > > if (rc < 0) { > > > - err("Couldn't discover IPv4 address: %s", > > > - strerror(-rc)); > > > + debug("Couldn't discover IPv4 address: %s", > > > + strerror(-rc)); > > > return 0; > > > } > > > } > > > @@ -677,6 +691,19 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4) > > > return ifi; > > > } > > > > > > +/** > > > + * conf_ip4_local() - Configure IPv4 addresses and attributes for local mode > > > + * @ip4: IPv4 context (will be written) > > > + */ > > > +static void conf_ip4_local(struct ip4_ctx *ip4) > > > +{ > > > + ip4->addr_seen = ip4->addr = IP4_LL_GUEST_ADDR; > > > + ip4->our_tap_addr = ip4->guest_gw = IP4_LL_GUEST_GW; > > > + ip4->prefix_len = IP4_LL_PREFIX_LEN; > > > + > > > + ip4->no_copy_addrs = ip4->no_copy_routes = true; > > > +} > > > + > > > /** > > > * conf_ip6() - Verify or detect IPv6 support, get relevant addresses > > > * @ifi: Host interface to attempt (0 to determine one) > > > @@ -693,15 +720,15 @@ static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6) > > > ifi = nl_get_ext_if(nl_sock, AF_INET6); > > > > > > if (!ifi) { > > > - info("Couldn't pick external interface: disabling IPv6"); > > > + debug("Failed to detect external interface for IPv6"); > > > return 0; > > > } > > > > > > if (IN6_IS_ADDR_UNSPECIFIED(&ip6->guest_gw)) { > > > rc = nl_route_get_def(nl_sock, ifi, AF_INET6, &ip6->guest_gw); > > > if (rc < 0) { > > > - err("Couldn't discover IPv6 gateway address: %s", > > > - strerror(-rc)); > > > + debug("Couldn't discover IPv6 gateway address: %s", > > > + strerror(-rc)); > > > return 0; > > > } > > > } > > > @@ -710,7 +737,7 @@ static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6) > > > IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ? &ip6->addr : NULL, > > > &prefix_len, &ip6->our_tap_ll); > > > if (rc < 0) { > > > - err("Couldn't discover IPv6 address: %s", strerror(-rc)); > > > + debug("Couldn't discover IPv6 address: %s", strerror(-rc)); > > > return 0; > > > } > > > > > > @@ -726,6 +753,17 @@ static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6) > > > return ifi; > > > } > > > > > > +/** > > > + * conf_ip6_local() - Configure IPv6 addresses and attributes for local mode > > > + * @ip6: IPv6 context (will be written) > > > + */ > > > +static void conf_ip6_local(struct ip6_ctx *ip6) > > > +{ > > > + ip6->our_tap_ll = ip6->guest_gw = IP6_LL_GUEST_GW; > > > + > > > + ip6->no_copy_addrs = ip6->no_copy_routes = true; > > > +} > > > + > > > /** > > > * usage() - Print usage, exit with given status code > > > * @name: Executable name > > > @@ -948,12 +986,14 @@ static void conf_print(const struct ctx *c) > > > char bufmac[ETH_ADDRSTRLEN], ifn[IFNAMSIZ]; > > > int i; > > > > > > - info("Template interface: %s%s%s%s%s", > > > - c->ifi4 ? if_indextoname(c->ifi4, ifn) : "", > > > - c->ifi4 ? " (IPv4)" : "", > > > - (c->ifi4 && c->ifi6) ? ", " : "", > > > - c->ifi6 ? if_indextoname(c->ifi6, ifn) : "", > > > - c->ifi6 ? " (IPv6)" : ""); > > > + if (c->ifi4 > 0 || c->ifi6 > 0) { > > > + info("Template interface: %s%s%s%s%s", > > > + c->ifi4 > 0 ? if_indextoname(c->ifi4, ifn) : "", > > > + c->ifi4 > 0 ? " (IPv4)" : "", > > > + (c->ifi4 && c->ifi6) ? ", " : "", > > > + c->ifi6 > 0 ? if_indextoname(c->ifi6, ifn) : "", > > > + c->ifi6 > 0 ? " (IPv6)" : ""); > > > + } > > > > > > if (*c->ip4.ifname_out || *c->ip6.ifname_out) { > > > info("Outbound interface: %s%s%s%s%s", > > > @@ -1024,9 +1064,9 @@ static void conf_print(const struct ctx *c) > > > > > > if (!c->no_ndp && !c->no_dhcpv6) > > > info("NDP/DHCPv6:"); > > > - else if (!c->no_ndp) > > > - info("DHCPv6:"); > > > else if (!c->no_dhcpv6) > > > + info("DHCPv6:"); > > > + else if (!c->no_ndp) > > > info("NDP:"); > > > else > > > goto dns6; > > > @@ -1735,8 +1775,20 @@ void conf(struct ctx *c, int argc, char **argv) > > > c->ifi6 = conf_ip6(ifi6, &c->ip6); > > > if ((!c->ifi4 && !c->ifi6) || > > > (*c->ip4.ifname_out && !c->ifi4) || > > > - (*c->ip6.ifname_out && !c->ifi6)) > > > - die("External interface not usable"); > > > > I guess a question is if the host has IPv4 but no IPv6 connectivity, > > do we want to disable IPv6 in the guest, or configure local-mode IPv6? > > That is something we can probably change without too much danger later > > on. > > I think we want to disable it by default, because the whole point here > is about permanently or temporarily disconnected setups, not what IP > versions are enabled on the host. If IPv4 is there, it's connected. Ok, that's reasonable. I don't think it should be too bad to change it later if we want to. > > > + (*c->ip6.ifname_out && !c->ifi6)) { > > > + info("No external interface as template, switch to local mode"); > > > + > > > + conf_ip4_local(&c->ip4); > > > + c->ifi4 = -1; > > > + > > > + conf_ip6_local(&c->ip6); > > > + c->ifi6 = -1; > > > + > > > + if (!*c->pasta_ifn) { > > > + strncpy(c->pasta_ifn, pasta_default_ifn, > > > + sizeof(c->pasta_ifn) - 1); > > > + } > > > + } > > > > > > if (c->ifi4 && !no_map_gw && > > > IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_host_loopback)) > > > @@ -1840,6 +1892,8 @@ void conf(struct ctx *c, int argc, char **argv) > > > if (!c->ifi6) { > > > c->no_ndp = 1; > > > c->no_dhcpv6 = 1; > > > + } else if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) { > > > + c->no_dhcpv6 = 1; > > > } > > > > > > if (!c->mtu) > > > diff --git a/passt.1 b/passt.1 > > > index f084978..f5cf8a4 100644 > > > --- a/passt.1 > > > +++ b/passt.1 > > > @@ -160,7 +160,9 @@ once for IPv6). > > > By default, assigned IPv4 and IPv6 addresses are taken from the host interfaces > > > with the first default route, if any, for the corresponding IP version. If no > > > default routes are available and there is any interface with any route for a > > > -given IP version, the first of these interfaces will be chosen instead. > > > +given IP version, the first of these interfaces will be chosen instead. If no > > > +such interface exists, the link-local address 169.254.2.1 is assigned for IPv4, > > > +and no additional address will be assigned for IPv6. > > > > > > .TP > > > .BR \-n ", " \-\-netmask " " \fImask > > > @@ -188,7 +190,9 @@ first default route, if any, for the corresponding IP version. If the default > > > route is a multipath one, the gateway is the first nexthop router returned by > > > the kernel which has the highest weight in the set of paths. If no default > > > routes are available and there is just one interface with any route, that > > > -interface will be chosen instead. > > > +interface will be chosen instead. If no such interface exists, the link-local > > > +address 169.254.2.2 is used for IPv4, and the link-local address fe80::1 is used > > > +for IPv6. > > > > > > Note: these addresses are also used as source address for packets directed to > > > the guest or to the target namespace having a loopback or local source address, > > > @@ -203,7 +207,9 @@ Default is to use the interfaces specified by \fB--outbound-if4\fR and > > > > > > If no interfaces are given, the interface with the first default routes for each > > > IP version is selected. If no default routes are available and there is just one > > > -interface with any route, that interface will be chosen instead. > > > +interface with any route, that interface will be chosen instead. If no such > > > +interface exists, host interfaces will be ignored for the purposes of assigning > > > +addresses and routes, and link-local addresses will be used instead. > > > > > > .TP > > > .BR \-o ", " \-\-outbound " " \fIaddr > > > @@ -222,7 +228,8 @@ derive IPv4 addresses and routes. > > > > > > By default, the interface given by the default route is selected. If no default > > > routes are available and there is just one interface with any route, that > > > -interface will be chosen instead. > > > +interface will be chosen instead. If no such interface exists, outbound sockets > > > +will not be bound to any specific interface. > > > > > > .TP > > > .BR \-\-outbound-if6 " " \fIname > > > @@ -232,7 +239,8 @@ derive IPv6 addresses and routes. > > > > > > By default, the interface given by the default route is selected. If no default > > > routes are available and there is just one interface with any route, that > > > -interface will be chosen instead. > > > +interface will be chosen instead. If no such interface exists, outbound sockets > > > +will not be bound to any specific interface. > > > > > > .TP > > > .BR \-D ", " \-\-dns " " \fIaddr > > > @@ -504,6 +512,7 @@ Default is \fBnone\fR. > > > .BR \-I ", " \-\-ns-ifname " " \fIname > > > Name of tap interface to be created in target namespace. > > > By default, the same interface name as the external, routable interface is used. > > > +If no such interface exists, the name \fItap0\fR will be used instead. > > > > > > .TP > > > .BR \-t ", " \-\-tcp-ports " " \fIspec > > > @@ -1032,6 +1041,20 @@ If the sending window cannot be queried, it will always be announced as the > > > current sending buffer size to guest or target namespace. This might affect > > > throughput of TCP connections. > > > > > > +.SS Local mode for disconnected setups > > > + > > > +If \fBpasst\fR and \fBpasta\fR fail to find a host interface with a configured > > > +address, other than loopback addresses, they will, obviously, not attempt to > > > +source addresses or routes from the host. > > > + > > > +In this case, unless configured otherwise, they will assign the IPv4 link-local > > > +address 169.254.2.1 to the guest or target namespace, and no IPv6 address. The > > > +notion of the guest or target namespace IPv6 address is derived from the first > > > +link-local address observed. > > > + > > > +Default gateways will be assigned as the link-local address 169.254.2.2 for > > > +IPv4, and as the link-local address fe80::1 for IPv6. > > > + > > > .SH LIMITATIONS > > > > > > Currently, IGMP/MLD proxying (RFC 4605) and support for SCTP (RFC 4960) are not > > > diff --git a/passt.h b/passt.h > > > index 72c7f72..799ee50 100644 > > > --- a/passt.h > > > +++ b/passt.h > > > @@ -202,10 +202,10 @@ struct ip6_ctx { > > > * @our_tap_mac: Pasta/passt's MAC on the tap link > > > * @guest_mac: MAC address of guest or namespace, seen or configured > > > * @hash_secret: 128-bit secret for siphash functions > > > - * @ifi4: Index of template interface for IPv4, 0 if IPv4 disabled > > > + * @ifi4: Template interface for IPv4, -1: none, 0: IPv4 disabled > > > * @ip: IPv4 configuration > > > * @dns_search: DNS search list > > > - * @ifi6: Index of template interface for IPv6, 0 if IPv6 disabled > > > + * @ifi6: Template interface for IPv6, -1: none, 0: IPv6 disabled > > > * @ip6: IPv6 configuration > > > * @pasta_ifn: Name of namespace interface for pasta > > > * @pasta_ifi: Index of namespace interface for pasta > > > @@ -258,12 +258,12 @@ struct ctx { > > > unsigned char guest_mac[ETH_ALEN]; > > > uint64_t hash_secret[2]; > > > > > > - unsigned int ifi4; > > > + int ifi4; > > > struct ip4_ctx ip4; > > > > > > struct fqdn dns_search[MAXDNSRCH]; > > > > > > - unsigned int ifi6; > > > + int ifi6; > > > struct ip6_ctx ip6; > > > > > > char pasta_ifn[IF_NAMESIZE]; > > > diff --git a/pasta.c b/pasta.c > > > index a117704..96dacc3 100644 > > > --- a/pasta.c > > > +++ b/pasta.c > > > @@ -369,8 +369,11 @@ void pasta_ns_conf(struct ctx *c) > > > 0, IFF_NOARP); > > > > > > if (c->ip6.no_copy_addrs) { > > > - rc = nl_addr_set(nl_sock_ns, c->pasta_ifi, > > > - AF_INET6, &c->ip6.addr, 64); > > > + if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) { > > > + rc = nl_addr_set(nl_sock_ns, > > > + c->pasta_ifi, AF_INET6, > > > + &c->ip6.addr, 64); > > > + } > > > } else { > > > rc = nl_addr_dup(nl_sock, c->ifi6, > > > nl_sock_ns, c->pasta_ifi, > > > diff --git a/tap.c b/tap.c > > > index 14d9b3d..5347df4 100644 > > > --- a/tap.c > > > +++ b/tap.c > > > @@ -803,6 +803,9 @@ resume: > > > if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen)) { > > > c->ip6.addr_seen = *saddr; > > > } > > > + > > > + if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) > > > + c->ip6.addr = *saddr; > > > > Hmm.. not entirely sure if this is a good idea, or whether we should > > instead keep the assigned address blank as an indication that we never > > assigned something, the guest just picked for itself. > > If you keep this blank, mapping mechanisms don't work as intended > anymore. Ah, --map-guest-addr specifically. > In v1, this was consistent with IPv4 as we always had a fixed address, > fe80::2. But we don't need to invent a particular address to assign to > the guest for IPv6, so we want to effectively behave as if we assigned > whatever the guest already picked. Ok. Good enough for the time being, anyway. So, comments considered Reviewed-by: David Gibson > > > > } else if (!IN6_IS_ADDR_UNSPECIFIED(saddr)){ > > > c->ip6.addr_seen = *saddr; > > > } > -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson