January 2026 - dev

Thoughts on interface modes / multiple guest addresses
by David Gibson 16 Jan '26

16 Jan '26

Hi Jon, As discussed on the call yesterday, I've written up my thoughts on what a bunch of the address semantics should be. Turns out I'd already done some of this at: https://pad.passt.top/p/InterfaceMode I've now updated to cover some more things, and considering the possibility of multiple guest addresses.. Turns out etherpad doesn't really do tables, so it's two sections for the two suggested modes, with matching subheadings. It's still very much a draft so: * It might be unclear - please ask me to clarify anything * It will have some mistakes - make your case if you think my proposed semantics don't make sense * It will be incomplete - feel free to add extra subheadings for anything you -- 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

3 14

PASST/PASST Dynamic Networking Features
by Jon Maloy 16 Jan '26

16 Jan '26

Hi all, Before going further with the implementation, I spent some time to understand the contents and implications of the various bugs/texts we have in this area. I then tried, to the best of my ability, to compile them into user stories, which I think might be a good format for our users to evaluate this. https://pad.passt.top/p/NetlinkMonitor Please have a look and give feedback! ///jon

2 1

[PATCH v4 02/14] conf, fwd: Keep a table of our port forwarding configuration
by David Gibson 16 Jan '26

16 Jan '26

At present, we set up forwarding as we parse the -t, and -u options, not keeping a persistent data structure with all the details. We do have some information in struct fwd_ports, but it doesn't capture all the nuance that the options do. As a first step to generalising our forwarding model, add a table of all the forwarding rules to struct fwd_ports. For now it covers only explicit forwards, not automatic, and we don't do anything with it other than print some additional debug information. We'll do more with it in future patches. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 80 ++++++++++++++++++++++++++++----------------- fwd.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ fwd.h | 38 +++++++++++++++++++++- 3 files changed, 188 insertions(+), 31 deletions(-) diff --git a/conf.c b/conf.c index dbff87c2..7ad09469 100644 --- a/conf.c +++ b/conf.c @@ -137,7 +137,7 @@ static int parse_port_range(const char *s, char **endptr, * @last: Last port to forward * @exclude: Bitmap of ports to exclude * @to: Port to translate @first to when forwarding - * @weak: Ignore errors, as long as at least one port is mapped + * @flags: Flags for forwarding entries */ static void conf_ports_range_except(const struct ctx *c, char optname, const char *optarg, struct fwd_ports *fwd, @@ -145,10 +145,11 @@ static void conf_ports_range_except(const struct ctx *c, char optname, const char *ifname, uint16_t first, uint16_t last, const uint8_t *exclude, uint16_t to, - bool weak) + uint8_t flags) { + unsigned delta = to - first; bool bound_one = false; - unsigned i; + unsigned base, i; int fd; if (first == 0) { @@ -172,37 +173,45 @@ static void conf_ports_range_except(const struct ctx *c, char optname, } } - for (i = first; i <= last; i++) { - if (bitmap_isset(exclude, i)) + for (base = first; base <= last; base++) { + if (bitmap_isset(exclude, base)) continue; - if (bitmap_isset(fwd->map, i)) { - warn( -"Altering mapping of already mapped port number: %s", optarg); - } + for (i = base; i <= last; i++) { + if (bitmap_isset(exclude, i)) + break; - bitmap_set(fwd->map, i); - fwd->delta[i] = to - first; + if (bitmap_isset(fwd->map, i)) { + warn( +"Altering mapping of already mapped port number: %s", optarg); + } - if (optname == 't') - fd = tcp_listen(c, PIF_HOST, addr, ifname, i); - else if (optname == 'u') - fd = udp_listen(c, PIF_HOST, addr, ifname, i); - else - /* No way to check in advance for -T and -U */ - fd = 0; + if (optname == 't') + fd = tcp_listen(c, PIF_HOST, addr, ifname, i); + else if (optname == 'u') + fd = udp_listen(c, PIF_HOST, addr, ifname, i); + else + /* No way to check in advance for -T and -U */ + fd = 0; + + if (fd == -ENFILE || fd == -EMFILE) { + die( +"Can't open enough sockets for port specifier: %s", + optarg); + } - if (fd == -ENFILE || fd == -EMFILE) { - die("Can't open enough sockets for port specifier: %s", - optarg); + if (fd >= 0) { + bound_one = true; + } else if (!(flags & FWD_WEAK)) { + die( +"Failed to bind port %u (%s) for option '-%c %s'", + i, strerror_(-fd), optname, optarg); + } } - if (fd >= 0) { - bound_one = true; - } else if (!weak) { - die("Failed to bind port %u (%s) for option '-%c %s'", - i, strerror_(-fd), optname, optarg); - } + fwd_rule_add(fwd, flags, addr, ifname, base, i - 1, + base + delta); + base = i - 1; } if (!bound_one) @@ -272,7 +281,7 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg, conf_ports_range_except(c, optname, optarg, fwd, NULL, NULL, 1, NUM_PORTS - 1, exclude, - 1, true); + 1, FWD_WEAK); return; } @@ -357,7 +366,7 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg, conf_ports_range_except(c, optname, optarg, fwd, addr, ifname, 1, NUM_PORTS - 1, exclude, - 1, true); + 1, FWD_WEAK); return; } @@ -390,7 +399,7 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg, addr, ifname, orig_range.first, orig_range.last, exclude, - mapped_range.first, false); + mapped_range.first, 0); } while ((p = next_chunk(p, ','))); return; @@ -1224,6 +1233,17 @@ dns6: info(" %s", c->dns_search[i].n); } } + + info("Inbound TCP forwarding:"); + fwd_rules_print(&c->tcp.fwd_in); + info("Inbound UDP forwarding:"); + fwd_rules_print(&c->udp.fwd_in); + if (c->mode == MODE_PASTA) { + info("Outbound TCP forwarding:"); + fwd_rules_print(&c->tcp.fwd_out); + info("Outbound UDP forwarding:"); + fwd_rules_print(&c->udp.fwd_out); + } } /** diff --git a/fwd.c b/fwd.c index 961c533f..e80312fb 100644 --- a/fwd.c +++ b/fwd.c @@ -13,6 +13,7 @@ * Author: David Gibson <david(a)gibson.dropbear.id.au> */ +#include <assert.h> #include <stdint.h> #include <errno.h> #include <fcntl.h> @@ -22,6 +23,8 @@ #include "util.h" #include "ip.h" +#include "siphash.h" +#include "inany.h" #include "fwd.h" #include "passt.h" #include "lineread.h" @@ -300,6 +303,20 @@ parse_err: warn("Unable to parse %s", PORT_RANGE_SYSCTL); } +/** + * fwd_rule_addr() - Return match address for a rule + * @rule: Forwarding rule + * + * Return: matching address for rule, NULL if it matches all addresses + */ +static const union inany_addr *fwd_rule_addr(const struct fwd_rule *rule) +{ + if (rule->flags & FWD_DUAL_STACK_ANY) + return NULL; + + return &rule->addr; +} + /** * fwd_port_is_ephemeral() - Is port number ephemeral? * @port: Port number @@ -313,6 +330,90 @@ bool fwd_port_is_ephemeral(in_port_t port) return (port >= fwd_ephemeral_min) && (port <= fwd_ephemeral_max); } +/** + * fwd_rule_add() - Add a rule to a forwarding table + * @fwd: Table to add to + * @flags: Flags for this entry + * @addr: Our address to forward (NULL for both 0.0.0.0 and ::) + * @ifname: Only forward from this interface name, if non-empty + * @first: First port number to forward + * @last: Last port number to forward + * @to: First port of target port range to map to + */ +void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, + const union inany_addr *addr, const char *ifname, + in_port_t first, in_port_t last, in_port_t to) +{ + /* Flags which can be set from the caller */ + const uint8_t allowed_flags = FWD_WEAK; + struct fwd_rule *new; + unsigned port; + + ASSERT(!(flags & ~allowed_flags)); + + if (fwd->count >= ARRAY_SIZE(fwd->rules)) + die("Too many port forwarding ranges"); + + new = &fwd->rules[fwd->count++]; + new->flags = flags; + + if (addr) { + new->addr = *addr; + } else { + new->addr = inany_any6; + new->flags |= FWD_DUAL_STACK_ANY; + } + + memset(new->ifname, 0, sizeof(new->ifname)); + if (ifname) { + if (strlen(ifname) + 1 > sizeof(new->ifname)) + die("Interface name %s is too long", ifname); + strncpy(new->ifname, ifname, sizeof(new->ifname)); + } + + ASSERT(first <= last); + new->first = first; + new->last = last; + + new->to = to; + + for (port = new->first; port <= new->last; port++) { + /* Fill in the legacy data structures to match the table */ + bitmap_set(fwd->map, port); + fwd->delta[port] = new->to - new->first; + } +} + +/** + * fwd_rules_print() - Print forwarding rules for debugging + * @fwd: Table to print + */ +void fwd_rules_print(const struct fwd_ports *fwd) +{ + unsigned i; + + for (i = 0; i < fwd->count; i++) { + const struct fwd_rule *rule = &fwd->rules[i]; + const char *percent = *rule->ifname ? "%" : ""; + char addr[INANY_ADDRSTRLEN]; + const char *weak = ""; + + inany_ntop(fwd_rule_addr(rule), addr, sizeof(addr)); + if (rule->flags & FWD_WEAK) + weak = " (best effort)"; + + if (rule->first == rule->last) { + info(" [%s]%s%s:%hu => %hu %s", + addr, percent, rule->ifname, + rule->first, rule->to, weak); + } else { + info(" [%s]%s%s:%hu-%hu => %hu-%hu %s", + addr, percent, rule->ifname, rule->first, rule->last, + rule->to, rule->last - rule->first + rule->to, weak); + } + } +} + /* See enum in kernel's include/net/tcp_states.h */ #define UDP_LISTEN 0x07 #define TCP_LISTEN 0x0a diff --git a/fwd.h b/fwd.h index 934bab33..d2a59c15 100644 --- a/fwd.h +++ b/fwd.h @@ -16,6 +16,33 @@ struct flowside; void fwd_probe_ephemeral(void); bool fwd_port_is_ephemeral(in_port_t port); +/** + * struct fwd_rule - Forwarding rule governing a range of ports + * @addr: Address to forward from + * @ifname: Interface to forward from + * @first: First port number to forward + * @last: Last port number to forward + * @to: Target port for @first, port n goes to @to + (n - @first) + * @flags: Flag mask + * FWD_DUAL_STACK_ANY - match any IPv4 or IPv6 address (@addr should be ::) + * FWD_WEAK - Don't give an error if binds fail for some forwards + * + * FIXME: @addr and @ifname currently ignored for outbound tables + */ +struct fwd_rule { + union inany_addr addr; + char ifname[IFNAMSIZ]; + in_port_t first; + in_port_t last; + in_port_t to; +#define FWD_DUAL_STACK_ANY BIT(0) +#define FWD_WEAK BIT(1) + uint8_t flags; +}; + +#define FWD_RULE_BITS 8 +#define MAX_FWD_RULES MAX_FROM_BITS(FWD_RULE_BITS) + /** * union fwd_listen_ref - information about a single listening socket * @port: Bound port number of the socket @@ -44,6 +71,8 @@ enum fwd_ports_mode { * @mode: Overall forwarding mode (all, none, auto, specific ports) * @scan4: /proc/net fd to scan for IPv4 ports when in AUTO mode * @scan6: /proc/net fd to scan for IPv6 ports when in AUTO mode + * @count: Number of forwarding rules + * @rules: Array of forwarding rules * @map: Bitmap describing which ports are forwarded * @delta: Offset between the original destination and mapped port number */ @@ -51,14 +80,21 @@ struct fwd_ports { enum fwd_ports_mode mode; int scan4; int scan6; + unsigned count; + struct fwd_rule rules[MAX_FWD_RULES]; uint8_t map[PORT_BITMAP_SIZE]; in_port_t delta[NUM_PORTS]; }; #define FWD_PORT_SCAN_INTERVAL 1000 /* ms */ +void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, + const union inany_addr *addr, const char *ifname, + in_port_t first, in_port_t last, in_port_t to); +void fwd_rules_print(const struct fwd_ports *fwd); + void fwd_scan_ports_init(struct ctx *c); -void fwd_scan_ports_timer(struct ctx *c, const struct timespec *now); +void fwd_scan_ports_timer(struct ctx * c, const struct timespec *now); bool nat_inbound(const struct ctx *c, const union inany_addr *addr, union inany_addr *translated); -- 2.52.0

2 4

[PATCH v4 00/14] Introduce forwarding table
by David Gibson 15 Jan '26

15 Jan '26

This creates a new data structure for recording our port forwarding: a table of individual forwarding rules. This is intended to replace the existing forwarding mode, map and delta structures. For now, only the delta[] array is removed. map is still used, but only for automatic forwards. Mode is still used, but only has significance during configuration. There's still a lot that can be done for flexible forwarding, but this introduces the core data structure, and does enough to fix at least one concrete defect with the current logic (bug 187). I think it would be a good point to give it a solid review and maybe merge. I'm aware that this is a very large complex series, that will be difficult to review. I think that's more or less inevitable implementing a feature as broad and complex as "flexible forwarding". If it helps at all, I'm fine if it's not reviewed all at once - I won't assume review is complete until either you say so, or I get comments or R-b on each patch. This applies on top of all 3 of my outstanding series in this area: "Allow listen functions to return fds", "Clean ups to epoll references" (v2) and "Small cleanups to splice forwarding logic". Changes in v5: * Numerous cosmetic changes * Re-arrange rule hinting to avoid coverity error David Gibson (14): inany: Extend inany_ntop() to treat NULL as a fully unspecified address conf, fwd: Keep a table of our port forwarding configuration conf: Accurately record ifname and address for outbound forwards conf, fwd: Record "auto" port forwards in forwarding table fwd: Make space to store listening sockets in forward table ip: Add ipproto_name() function fwd, tcp, udp: Set up listening sockets based on forward table tcp, udp: Remove old auto-forwarding socket arrays conf, fwd: Check forwarding table for conflicting rules fwd: Generate auto-forward exclusions from socket fd tables flow, fwd: Consult rules table when forwarding a new flow from socket fwd: Remap ports based directly on forwarding rule fwd, tcp, udp: Add forwarding rule to listening socket epoll references flow, fwd: Optimise forwarding rule lookup using epoll ref when possible conf.c | 118 +++++++++------ flow.c | 55 +++++-- flow_table.h | 2 +- fwd.c | 401 ++++++++++++++++++++++++++++++++++++++++++++++--- fwd.h | 72 ++++++++- icmp.c | 2 +- inany.c | 28 +++- inany.h | 1 + ip.c | 26 ++++ ip.h | 1 + tcp.c | 156 ++----------------- tcp.h | 6 +- udp.c | 149 +++--------------- udp.h | 7 +- udp_flow.c | 14 +- udp_flow.h | 2 +- udp_internal.h | 4 +- 17 files changed, 663 insertions(+), 381 deletions(-) -- 2.52.0

1 10

[PATCH v4 04/14] conf, fwd: Record "auto" port forwards in forwarding table
by David Gibson 15 Jan '26

15 Jan '26

Currently the forwarding table records details of explicit port forwards, but nothing for -[tTuU] auto. That looks a little odd on the debug output, and will be a problem for future changes. Extend the forward table to have rules for auto-scanned forwards, using a new FWD_SCAN flag. For now the mechanism of auto port forwarding isn't updated, and we will only create a single FWD_SCAN rule per protocol and direction. We'll better integrate auto scanning with other forward table mechanics in future. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 31 ++++++++++++++++++++++++++----- fwd.c | 21 +++++++++++++-------- fwd.h | 2 ++ 3 files changed, 41 insertions(+), 13 deletions(-) diff --git a/conf.c b/conf.c index 475dbe04..fb6a8118 100644 --- a/conf.c +++ b/conf.c @@ -135,7 +135,7 @@ static int parse_port_range(const char *s, char **endptr, * @ifname: Listening interface * @first: First port to forward * @last: Last port to forward - * @exclude: Bitmap of ports to exclude + * @exclude: Bitmap of ports to exclude (may be NULL) * @to: Port to translate @first to when forwarding * @flags: Flags for forwarding entries */ @@ -168,11 +168,11 @@ static void conf_ports_range_except(const struct ctx *c, char optname, } for (base = first; base <= last; base++) { - if (bitmap_isset(exclude, base)) + if (exclude && bitmap_isset(exclude, base)) continue; for (i = base; i <= last; i++) { - if (bitmap_isset(exclude, i)) + if (exclude && bitmap_isset(exclude, i)) break; if (bitmap_isset(fwd->map, i)) { @@ -180,9 +180,9 @@ static void conf_ports_range_except(const struct ctx *c, char optname, "Altering mapping of already mapped port number: %s", optarg); } - if (optname == 't') + if (!(flags & FWD_SCAN) && optname == 't') fd = tcp_listen(c, PIF_HOST, addr, ifname, i); - else if (optname == 'u') + else if (!(flags & FWD_SCAN) && optname == 'u') fd = udp_listen(c, PIF_HOST, addr, ifname, i); else /* No way to check in advance for -T and -U */ @@ -2200,6 +2200,27 @@ void conf(struct ctx *c, int argc, char **argv) if (!c->udp.fwd_out.mode) c->udp.fwd_out.mode = fwd_default; + if (c->tcp.fwd_in.mode == FWD_AUTO) { + conf_ports_range_except(c, 't', "auto", &c->tcp.fwd_in, + NULL, NULL, 1, NUM_PORTS - 1, + NULL, 1, FWD_SCAN); + } + if (c->tcp.fwd_out.mode == FWD_AUTO) { + conf_ports_range_except(c, 'T', "auto", &c->tcp.fwd_out, + NULL, "lo", 1, NUM_PORTS - 1, + NULL, 1, FWD_SCAN); + } + if (c->udp.fwd_in.mode == FWD_AUTO) { + conf_ports_range_except(c, 'u', "auto", &c->udp.fwd_in, + NULL, NULL, 1, NUM_PORTS - 1, + NULL, 1, FWD_SCAN); + } + if (c->udp.fwd_out.mode == FWD_AUTO) { + conf_ports_range_except(c, 'U', "auto", &c->udp.fwd_out, + NULL, "lo", 1, NUM_PORTS - 1, + NULL, 1, FWD_SCAN); + } + if (!c->quiet) conf_print(c); } diff --git a/fwd.c b/fwd.c index e80312fb..588bf24a 100644 --- a/fwd.c +++ b/fwd.c @@ -345,7 +345,7 @@ void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, in_port_t first, in_port_t last, in_port_t to) { /* Flags which can be set from the caller */ - const uint8_t allowed_flags = FWD_WEAK; + const uint8_t allowed_flags = FWD_WEAK | FWD_SCAN; struct fwd_rule *new; unsigned port; @@ -379,7 +379,8 @@ void fwd_rule_add(struct fwd_ports *fwd, uint8_t flags, for (port = new->first; port <= new->last; port++) { /* Fill in the legacy data structures to match the table */ - bitmap_set(fwd->map, port); + if (!(new->flags & FWD_SCAN)) + bitmap_set(fwd->map, port); fwd->delta[port] = new->to - new->first; } } @@ -395,21 +396,25 @@ void fwd_rules_print(const struct fwd_ports *fwd) for (i = 0; i < fwd->count; i++) { const struct fwd_rule *rule = &fwd->rules[i]; const char *percent = *rule->ifname ? "%" : ""; + const char *weak = "", *scan = ""; char addr[INANY_ADDRSTRLEN]; - const char *weak = ""; inany_ntop(fwd_rule_addr(rule), addr, sizeof(addr)); if (rule->flags & FWD_WEAK) weak = " (best effort)"; + if (rule->flags & FWD_SCAN) + scan = " (auto-scan)"; if (rule->first == rule->last) { - info(" [%s]%s%s:%hu => %hu %s", + info(" [%s]%s%s:%hu => %hu %s%s", addr, percent, rule->ifname, - rule->first, rule->to, weak); + rule->first, rule->to, weak, scan); } else { - info(" [%s]%s%s:%hu-%hu => %hu-%hu %s", - addr, percent, rule->ifname, rule->first, rule->last, - rule->to, rule->last - rule->first + rule->to, weak); + info(" [%s]%s%s:%hu-%hu => %hu-%hu %s%s", + addr, percent, rule->ifname, + rule->first, rule->last, + rule->to, rule->last - rule->first + rule->to, + weak, scan); } } } diff --git a/fwd.h b/fwd.h index d2a59c15..cc7e0aca 100644 --- a/fwd.h +++ b/fwd.h @@ -26,6 +26,7 @@ bool fwd_port_is_ephemeral(in_port_t port); * @flags: Flag mask * FWD_DUAL_STACK_ANY - match any IPv4 or IPv6 address (@addr should be ::) * FWD_WEAK - Don't give an error if binds fail for some forwards + * FWD_SCAN - Only forward if the matching port in the target is listening * * FIXME: @addr and @ifname currently ignored for outbound tables */ @@ -37,6 +38,7 @@ struct fwd_rule { in_port_t to; #define FWD_DUAL_STACK_ANY BIT(0) #define FWD_WEAK BIT(1) +#define FWD_SCAN BIT(2) uint8_t flags; }; -- 2.52.0

1 0

[PATCH v4 03/14] conf: Accurately record ifname and address for outbound forwards
by David Gibson 15 Jan '26

15 Jan '26

-T and -U options don't allow specifying a listening address. Usually this will listen on *%lo in the guest. However on kernels without unprivileged SO_BINDTODEVICE that's not possible so we instead listen separately on 127.0.0.1 and ::1. Currently that's handled at the point we actually set up the listens, we record both address and ifname as NULL in the forwarding table entry. That will cause trouble for future extensions we want, so update this to accurately create the forwarding table: either a single rule with ifname == "lo" or two rules with addresses of 127.0.0.1 and ::1. As a bonus, this gives the user a warning if they specify an explicit outbound forwarding on a kernel without SO_BINDTODEVICE. The existing warning for missing SO_BINDTODEVICE incorrectly covered only the case of -T auto or -U auto. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 38 ++++++++++++++++++++++++++++++-------- 1 file changed, 30 insertions(+), 8 deletions(-) diff --git a/conf.c b/conf.c index 7ad09469..475dbe04 100644 --- a/conf.c +++ b/conf.c @@ -157,12 +157,6 @@ static void conf_ports_range_except(const struct ctx *c, char optname, optname, optarg); } - if (ifname && c->no_bindtodevice) { - die( -"Device binding for '-%c %s' unsupported (requires kernel 5.7+)", - optname, optarg); - } - if (addr) { if (!c->ifi4 && inany_v4(addr)) { die("IPv4 is disabled, can't use -%c %s", @@ -209,8 +203,27 @@ static void conf_ports_range_except(const struct ctx *c, char optname, } } - fwd_rule_add(fwd, flags, addr, ifname, base, i - 1, - base + delta); + if ((optname == 'T' || optname == 'U') && c->no_bindtodevice) { + /* FIXME: Once the fwd bitmaps are removed, move this + * workaround to the caller + */ + ASSERT(!addr && ifname && !strcmp(ifname, "lo")); + warn( +"SO_BINDTODEVICE unavailable, forwarding only 127.0.0.1 and ::1 for '-%c %s'", + optname, optarg); + + if (c->ifi4) { + fwd_rule_add(fwd, flags, &inany_loopback4, NULL, + base, i - 1, base + delta); + } + if (c->ifi6) { + fwd_rule_add(fwd, flags, &inany_loopback6, NULL, + base, i - 1, base + delta); + } + } else { + fwd_rule_add(fwd, flags, addr, ifname, + base, i - 1, base + delta); + } base = i - 1; } @@ -357,6 +370,15 @@ static void conf_ports(const struct ctx *c, char optname, const char *optarg, } } while ((p = next_chunk(p, ','))); + if (ifname && c->no_bindtodevice) { + die( +"Device binding for '-%c %s' unsupported (requires kernel 5.7+)", + optname, optarg); + } + /* Outbound forwards come from guest loopback */ + if ((optname == 'T' || optname == 'U') && !ifname) + ifname = "lo"; + if (exclude_only) { /* Exclude ephemeral ports */ for (i = 0; i < NUM_PORTS; i++) -- 2.52.0

1 0

[PATCH v4 01/14] inany: Extend inany_ntop() to treat NULL as a fully unspecified address
by David Gibson 15 Jan '26

15 Jan '26

In a number of places we're using a convention that a NULL inany represents a dual-stack unspecified address, that is one which includes both 0.0.0.0 and ::. Extend inany_ntop() to handle that convention, representing it as "*". Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> Reviewed-by: Laurent Vivier <lvivier(a)redhat.com> --- inany.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/inany.c b/inany.c index 7680439d..87a4d8b6 100644 --- a/inany.c +++ b/inany.c @@ -22,7 +22,7 @@ const union inany_addr inany_loopback4 = INANY_INIT4(IN4ADDR_LOOPBACK_INIT); const union inany_addr inany_any4 = INANY_INIT4(IN4ADDR_ANY_INIT); /** inany_ntop - Convert an IPv[46] address to text format - * @src: IPv[46] address + * @src: IPv[46] address (NULL for unspecified) * @dst: output buffer, minimum INANY_ADDRSTRLEN bytes * @size: size of buffer at @dst * @@ -30,9 +30,12 @@ const union inany_addr inany_any4 = INANY_INIT4(IN4ADDR_ANY_INIT); */ const char *inany_ntop(const union inany_addr *src, char *dst, socklen_t size) { - const struct in_addr *v4 = inany_v4(src); + const struct in_addr *v4; + + if (!src) + return strncpy(dst, "*", size); - if (v4) + if ((v4 = inany_v4(src))) return inet_ntop(AF_INET, v4, dst, size); return inet_ntop(AF_INET6, &src->a6, dst, size); -- 2.52.0

1 0

[PATCH] conf, pasta: Add --no-tap option
by Yumei Huang 14 Jan '26

14 Jan '26

This patch introduces a mode where we only forward loopback connections and traffic between two namespaces (via the loopback interface, 'lo'), without a tap device. With this, podman can support forwarding ::1 in custom networks when using rootlesskit for forwarding ports. In --no-tap mode, --host-lo-to-ns-lo, --no-icmp and --no-ra is automatically enabled. Options requiring a tap device (--ns-ifname, --ns-mac-addr, --config-net, --outbound-if4/6) are rejected. Link: https://bugs.passt.top/show_bug.cgi?id=149 Signed-off-by: Yumei Huang <yuhuang(a)redhat.com> --- conf.c | 56 +++++++++++++++++++++++++++++++++++++++++--------------- fwd.c | 3 +++ passt.1 | 5 +++++ passt.h | 2 ++ pasta.c | 3 +++ tap.c | 11 +++++++---- 6 files changed, 61 insertions(+), 19 deletions(-) diff --git a/conf.c b/conf.c index 84ae12b..353d0a5 100644 --- a/conf.c +++ b/conf.c @@ -1049,7 +1049,8 @@ pasta_opts: " --no-copy-addrs DEPRECATED:\n" " Don't copy all addresses to namespace\n" " --ns-mac-addr ADDR Set MAC address on tap interface\n" - " --no-splice Disable inbound socket splicing\n"); + " --no-splice Disable inbound socket splicing\n" + " --no-tap Don't create tap device\n"); passt_exit(status); } @@ -1451,6 +1452,7 @@ void conf(struct ctx *c, int argc, char **argv) {"no-ndp", no_argument, &c->no_ndp, 1 }, {"no-ra", no_argument, &c->no_ra, 1 }, {"no-splice", no_argument, &c->no_splice, 1 }, + {"no-tap", no_argument, &c->no_tap, 1 }, {"freebind", no_argument, &c->freebind, 1 }, {"no-map-gw", no_argument, &no_map_gw, 1 }, {"ipv4-only", no_argument, NULL, '4' }, @@ -1947,8 +1949,11 @@ void conf(struct ctx *c, int argc, char **argv) } } while (name != -1); - if (c->mode != MODE_PASTA) + if (c->mode != MODE_PASTA) { c->no_splice = 1; + if (c->no_tap) + die("--no-tap is for pasta mode only"); + } if (c->mode == MODE_PASTA && !c->pasta_conf_ns) { if (copy_routes_opt) @@ -1957,6 +1962,25 @@ void conf(struct ctx *c, int argc, char **argv) die("--no-copy-addrs needs --config-net"); } + if (c->mode == MODE_PASTA && c->no_tap) { + if (c->no_splice) + die("--no-tap is incompatible with --no-splice"); + if (*c->ip4.ifname_out || *c->ip6.ifname_out) + die("--no-tap is incompatible with --outbound-if4/6"); + if (*c->pasta_ifn) + die("--no-tap is incompatible with --ns-ifname"); + if (*c->guest_mac) + die("--no-tap is incompatible with --ns-mac-addr"); + if (c->pasta_conf_ns) + die("--no-tap is incompatible with --config-net"); + + c->host_lo_to_ns_lo = 1; + c->no_icmp = 1; + c->no_ra = 1; + c->no_dns = 1; + c->no_dns_search = 1; + } + if (!ifi4 && *c->ip4.ifname_out) ifi4 = if_nametoindex(c->ip4.ifname_out); @@ -1980,9 +2004,9 @@ void conf(struct ctx *c, int argc, char **argv) log_conf_parsed = true; /* Stop printing everything */ nl_sock_init(c, false); - if (!v6_only) + if (!v6_only && !c->no_tap) c->ifi4 = conf_ip4(ifi4, &c->ip4); - if (!v4_only) + if (!v4_only && !c->no_tap) c->ifi6 = conf_ip6(ifi6, &c->ip6); if (c->ifi4 && c->mtu < IPV4_MIN_MTU) { @@ -1998,30 +2022,32 @@ void conf(struct ctx *c, int argc, char **argv) (*c->ip6.ifname_out && !c->ifi6)) die("External interface not usable"); - if (!c->ifi4 && !c->ifi6 && !*c->pasta_ifn) { + if (!c->ifi4 && !c->ifi6 && !*c->pasta_ifn && !c->no_tap) { strncpy(c->pasta_ifn, pasta_default_ifn, sizeof(c->pasta_ifn) - 1); } if (!c->ifi4 && !v6_only) { - info("IPv4: no external interface as template, use local mode"); - - conf_ip4_local(&c->ip4); + if (!c->no_tap) { + info("IPv4: no external interface as template, use local mode"); + conf_ip4_local(&c->ip4); + } c->ifi4 = -1; } if (!c->ifi6 && !v4_only) { - info("IPv6: no external interface as template, use local mode"); - - conf_ip6_local(&c->ip6); + if (!c->no_tap) { + info("IPv6: no external interface as template, use local mode"); + conf_ip6_local(&c->ip6); + } c->ifi6 = -1; } - if (c->ifi4 && !no_map_gw && + if (c->ifi4 > 0 && !no_map_gw && IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_host_loopback)) c->ip4.map_host_loopback = c->ip4.guest_gw; - if (c->ifi6 && !no_map_gw && + if (c->ifi6 > 0 && !no_map_gw && IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_host_loopback)) c->ip6.map_host_loopback = c->ip6.guest_gw; @@ -2116,10 +2142,10 @@ void conf(struct ctx *c, int argc, char **argv) conf_ports(c, name, optarg, &c->udp.fwd_out); } while (name != -1); - if (!c->ifi4) + if (c->ifi4 <= 0) c->no_dhcp = 1; - if (!c->ifi6) { + if (c->ifi6 <= 0) { c->no_ndp = 1; c->no_dhcpv6 = 1; } else if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) { diff --git a/fwd.c b/fwd.c index 44a0e10..2f4a89a 100644 --- a/fwd.c +++ b/fwd.c @@ -780,6 +780,9 @@ uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto, return PIF_SPLICE; } + if (c->no_tap) + return PIF_NONE; + if (!nat_inbound(c, &ini->eaddr, &tgt->oaddr)) { if (inany_v4(&ini->eaddr)) { if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.our_tap_addr)) diff --git a/passt.1 b/passt.1 index db0d662..2d643f7 100644 --- a/passt.1 +++ b/passt.1 @@ -755,6 +755,11 @@ Default is to let the tap driver build a pseudorandom hardware address. Disable the bypass path for inbound, local traffic. See the section \fBHandling of local traffic in pasta\fR in the \fBNOTES\fR for more details. +.TP +.BR \-\-no-tap +Do not create a tap device in the namespace. In this mode, only local loopback +traffic between namespaces is forwarded using splice. + .SH EXAMPLES .SS \fBpasta diff --git a/passt.h b/passt.h index 79d01dd..0c1ec4c 100644 --- a/passt.h +++ b/passt.h @@ -200,6 +200,7 @@ struct ip6_ctx { * @no_ndp: Disable NDP handler altogether * @no_ra: Disable router advertisements * @no_splice: Disable socket splicing for inbound traffic + * @no_tap: Do not create tap device * @host_lo_to_ns_lo: Map host loopback addresses to ns loopback addresses * @freebind: Allow binding of non-local addresses for forwarding * @low_wmem: Low probed net.core.wmem_max @@ -277,6 +278,7 @@ struct ctx { int no_ndp; int no_ra; int no_splice; + int no_tap; int host_lo_to_ns_lo; int freebind; diff --git a/pasta.c b/pasta.c index 0ddd6b0..3510ec5 100644 --- a/pasta.c +++ b/pasta.c @@ -316,6 +316,9 @@ void pasta_ns_conf(struct ctx *c) die("Couldn't bring up loopback interface in namespace: %s", strerror_(-rc)); + if (c->no_tap) + return; + /* Get or set MAC in target namespace */ if (MAC_IS_ZERO(c->guest_mac)) nl_link_get_mac(nl_sock_ns, c->pasta_ifi, c->guest_mac); diff --git a/tap.c b/tap.c index 9d1344b..9b4eedc 100644 --- a/tap.c +++ b/tap.c @@ -1491,13 +1491,16 @@ static int tap_ns_tun(void *arg) */ static void tap_sock_tun_init(struct ctx *c) { - NS_CALL(tap_ns_tun, c); - if (c->fd_tap == -1) - die("Failed to set up tap device in namespace"); + if (!c->no_tap) { + NS_CALL(tap_ns_tun, c); + if (c->fd_tap == -1) + die("Failed to set up tap device in namespace"); + } pasta_ns_conf(c); - tap_start_connection(c); + if (!c->no_tap) + tap_start_connection(c); } /** -- 2.49.0

4 23

[PATCH 3/3] igmp: Remove apparently unneeded suppression
by David Gibson 14 Jan '26

14 Jan '26

cppcheck-2.19.1 complains that the unusedFunction suppression in igmp.c doesn't match. That seems like a cppcheck bug, because the function clearly *is* unused. The function exists because otherwise the compiler fails because "ISO C forbids an empty translation unit". mld.c contains an identical unused definition for the same reason, but without the suppression. It doesn't seem to have caused unusedFunction warnings, so maybe cppcheck counts the non-empty translation unit requirement as a "use" of the function? In any case, since omitting the suppression in mld.c seems to be fine, do the same in igmp.c to stop the complaints. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- igmp.c | 1 - 1 file changed, 1 deletion(-) diff --git a/igmp.c b/igmp.c index 0e775843..a3971fc6 100644 --- a/igmp.c +++ b/igmp.c @@ -13,5 +13,4 @@ */ /* TO BE IMPLEMENTED */ -/* cppcheck-suppress unusedFunction */ __attribute__((__unused__)) static void unused(void) { } -- 2.52.0

2 2

[PATCH v3 00/14] Introduce forwarding table
by David Gibson 14 Jan '26

14 Jan '26

This creates a new data structure for recording our port forwarding: a table of individual forwarding rules. This is intended to replace the existing forwarding mode, map and delta structures. For now, only the delta[] array is removed. map is still used, but only for automatic forwards. Mode is still used, but only has significance during configuration. There's still a lot that can be done for flexible forwarding, but this introduces the core data structure, and does enough to fix at least one concrete defect with the current logic (bug 187). I think it would be a good point to give it a solid review and maybe merge. I'm aware that this is a very large complex series, that will be difficult to review. I think that's more or less inevitable implementing a feature as broad and complex as "flexible forwarding". If it helps at all, I'm fine if it's not reviewed all at once - I won't assume review is complete until either you say so, or I get comments or R-b on each patch. This applies on top of all 3 of my outstanding series in this area: "Allow listen functions to return fds", "Clean ups to epoll references" (v2) and "Small cleanups to splice forwarding logic". David Gibson (14): inany: Extend inany_ntop() to treat NULL as a fully unspecified address conf, fwd: Keep a table of our port forwarding configuration conf: Accurately record ifname and address for outbound forwards conf, fwd: Record "auto" port forwards in forwarding table fwd: Make space to store listening sockets in forward table ip: Add ipproto_name() function fwd, tcp, udp: Set up listening sockets based on forward table tcp, udp: Remove old auto-forwarding socket arrays conf, fwd: Check forwarding table for conflicting rules fwd: Generate auto-forward exclusions from socket fd tables flow, fwd: Consult rules table when forwarding a new flow from socket fwd: Remap ports based directly on forwarding rule fwd, tcp, udp: Add forwarding rule to listening socket epoll references flow, fwd: Optimise forwarding rule lookup using epoll ref when possible conf.c | 118 +++++++++------ flow.c | 59 ++++++-- flow_table.h | 2 +- fwd.c | 379 ++++++++++++++++++++++++++++++++++++++++++++++--- fwd.h | 68 ++++++++- icmp.c | 2 +- inany.c | 28 +++- inany.h | 1 + ip.c | 26 ++++ ip.h | 2 + tcp.c | 154 ++------------------ tcp.h | 6 +- udp.c | 147 +++---------------- udp.h | 7 +- udp_flow.c | 14 +- udp_flow.h | 2 +- udp_internal.h | 4 +- 17 files changed, 641 insertions(+), 378 deletions(-) -- 2.52.0

3 39