July 2026 - dev

[PATCH v4 0/4] Add --dhcp-boot and --dhcp-opt options
by Anshu Kumari 01 Jul '26

01 Jul '26

This series adds support for custom DHCP options in passt, enabling network boot (PXE/UEFI HTTP Boot) and arbitrary DHCP option injection. Two new command-line flags are introduced: --dhcp-boot URL Sets the boot file URL (DHCP option 67 and the legacy boot file field) --dhcp-opt CODE,VALUE Sets any DHCP option by numeric code, with type-aware parsing per RFC 2132 The DHCP reply path is extended with option overload support (RFC 2132 option 52), allowing options to overflow into the file and sname fields when the standard options area is full. v4: Restructured series from 6 patches to 4: - 1/4 refactor fill_one() - 2/4 option overload - 3/4 --dhcp-opt with parser and man page - 4/4 --dhcp-boot with man page Anshu Kumari (4): dhcp: Refactor fill_one() to operate on a generic buffer dhcp: Add option overload dhcp: Add --dhcp-opt with option table and value parser conf: Add --dhcp-boot command-line option conf.c | 50 ++++++++- dhcp.c | 321 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- dhcp.h | 2 + passt.1 | 49 +++++++++ passt.h | 6 ++ 5 files changed, 407 insertions(+), 21 deletions(-) -- 2.54.0

3 17

[PATCH v2 0/2] dhcpv6: Add --dhcpv6-opt for custom DHCPv6 options
by Anshu Kumari 01 Jul '26

01 Jul '26

This series adds a --dhcpv6-opt CODE,VALUE command-line option to inject custom options into DHCPv6 replies, complementing the existing --dhcp-opt support for DHCPv4. The primary use case is UEFI HTTP Boot, which requires Vendor Class (option 16) with the correct enterprise-number + length-prefixed wire encoding per RFC 8415 Section 21.16, and Boot File URL (option 59). Value formats are determined automatically from the option code via a type table. Supported types include plain strings, IPv6 addresses (single and list), 8/16/32-bit integers, vendor class (ENTERPRISE:DATA), and length-prefixed string lists. Anshu Kumari (2): dhcpv6: Add --dhcpv6-opt with option type table and value parser dhcpv6: Inject custom options into DHCPv6 replies conf.c | 60 ++++++++++++- dhcpv6.c | 253 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ dhcpv6.h | 2 + passt.1 | 31 +++++++ passt.h | 12 +++ 5 files changed, 357 insertions(+), 1 deletion(-) -- 2.54.0

3 7

[PATCH] isolation: Add --use-chroot-fallback option
by Mateusz Andrzejewski 01 Jul '26

01 Jul '26

For integrations, which use rootfs (tmpfs, initramfs), it is not allowed to use pivot_root(). It results with invalid argument (EINVAL) error. Introduce --use-chroot-fallback option as a workaround with MS_MOVE + chroot(). Due to weaker isolation of chroot() method (we don't umount old root), user has tu explicitly enable fallback with the new option. First, always try to sandbox with pivot_root(). In both cases the new root is placed into an empty tmpfs. For the solution to work we keep CAP_SYS_CHROOT capability, which is dropped at the end of the isolate_prefork() function. Signed-off-by: Mateusz Andrzejewski <mateusz.andrzejewski(a)mikronika.com.pl> --- conf.c | 9 ++++++-- isolation.c | 63 ++++++++++++++++++++++++++++++++++++++++++++--------- isolation.h | 2 +- passt.h | 2 ++ 4 files changed, 63 insertions(+), 13 deletions(-) diff --git a/conf.c b/conf.c index 4755a9f..fe4d5e9 100644 --- a/conf.c +++ b/conf.c @@ -654,6 +654,7 @@ static void usage(const char *name, FILE *f, int status) " --no-ra Disable router advertisements\n" " --freebind Bind to any address for forwarding\n" " --no-map-gw Don't map gateway address to host\n" + " --use-chroot-fallback Use chroot in case pivot_root fails\n" " -4, --ipv4-only Enable IPv4 operation only\n" " -6, --ipv6-only Enable IPv6 operation only\n" " -t, --tcp-ports SPEC TCP port forwarding to %s\n" @@ -1158,7 +1159,7 @@ static void conf_sock_listen(const struct ctx *c) */ void conf(struct ctx *c, int argc, char **argv) { - int netns_only = 0, no_map_gw = 0; + int netns_only = 0, no_map_gw = 0, use_chroot_fallback = 0; const struct option options[] = { {"debug", no_argument, NULL, 'd' }, {"quiet", no_argument, NULL, 'q' }, @@ -1192,6 +1193,7 @@ void conf(struct ctx *c, int argc, char **argv) {"splice-only", no_argument, &c->splice_only, 1 }, {"freebind", no_argument, &c->freebind, 1 }, {"no-map-gw", no_argument, &no_map_gw, 1 }, + {"use-chroot-fallback", no_argument, &use_chroot_fallback, 1 }, {"ipv4-only", no_argument, NULL, '4' }, {"ipv6-only", no_argument, NULL, '6' }, {"one-off", no_argument, NULL, '1' }, @@ -1777,6 +1779,8 @@ void conf(struct ctx *c, int argc, char **argv) c->no_dns_search = 1; } + c->use_chroot_fallback = use_chroot_fallback; + if (!ifi4 && *c->ip4.ifname_out) ifi4 = if_nametoindex(c->ip4.ifname_out); @@ -1879,7 +1883,8 @@ void conf(struct ctx *c, int argc, char **argv) conf_open_files(c); /* Before any possible setuid() / setgid() */ - isolate_user(uid, gid, !netns_only, userns, c->mode); + isolate_user(uid, gid, !netns_only, userns, c->mode, + c->use_chroot_fallback); if (c->no_icmp) c->no_ndp = 1; diff --git a/isolation.c b/isolation.c index 7e6225d..4e6fd32 100644 --- a/isolation.c +++ b/isolation.c @@ -166,6 +166,31 @@ static void clamp_caps(void) die_perror("Couldn't drop inheritable capabilities"); } +/** + * move_root() - Use chroot instead of pivot_root for sandboxing. + * + * Return: negative error code on failure, zero on success. + */ +static int move_root(void) +{ + if (mount(TMPDIR, "/", "", MS_MOVE, "")) { + err_perror("Failed to move root into empty tmpfs"); + return -errno; + } + + if (chroot(".")) { + err_perror("Failed to chroot into empty tmpfs"); + return -errno; + } + + if (chdir("/")) { + err_perror("Failed to change directory into new root"); + return -errno; + } + + return 0; +} + /** * isolate_initial() - Early, mostly config independent self isolation * @argc: Argument count @@ -201,8 +226,8 @@ void isolate_initial(int argc, char **argv) * isolate_prefork(). */ keep = BIT(CAP_NET_BIND_SERVICE) | BIT(CAP_SETUID) | BIT(CAP_SETGID) | - BIT(CAP_SYS_ADMIN) | BIT(CAP_NET_ADMIN) | BIT(CAP_DAC_OVERRIDE); - + BIT(CAP_SYS_ADMIN) | BIT(CAP_NET_ADMIN) | BIT(CAP_DAC_OVERRIDE) | + BIT(CAP_SYS_CHROOT); /* Since Linux 5.12, if we want to update /proc/self/uid_map to create * a mapping from UID 0, which only happens with pasta spawning a child * from a non-init user namespace (pasta can't run as root), we need to @@ -225,6 +250,7 @@ void isolate_initial(int argc, char **argv) * @use_userns: Whether to join or create a userns * @userns: userns path to enter, may be empty * @mode: Mode (passt or pasta) + * @use_chroot_fallback: Whether to use chroot() as fallback for sandboxing. * * Should: * - set our final UID and GID @@ -233,7 +259,7 @@ void isolate_initial(int argc, char **argv) * - remove filesystem access (we need that for further setup) */ void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns, - enum passt_modes mode) + enum passt_modes mode, bool use_chroot_fallback) { uint64_t ns_caps = 0; @@ -277,6 +303,13 @@ void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns, * netns */ ns_caps |= BIT(CAP_SYS_ADMIN); + + /* Keep CAP_SYS_CHROOT, so we can fallback to chroot + * in case of use-chroot-fallback option being enabled + */ + if (use_chroot_fallback) + ns_caps |= BIT(CAP_SYS_CHROOT); + if (mode == MODE_PASTA) { /* Keep CAP_NET_ADMIN, so we can configure the if */ ns_caps |= BIT(CAP_NET_ADMIN); @@ -310,6 +343,7 @@ int isolate_prefork(const struct ctx *c) { int flags = CLONE_NEWIPC | CLONE_NEWNS | CLONE_NEWUTS; uint64_t ns_caps = 0; + int result = -1; /* If we run in foreground, we have no chance to actually move to a new * PID namespace. For passt, use CLONE_NEWPID anyway, in case somebody @@ -331,7 +365,7 @@ int isolate_prefork(const struct ctx *c) if (mount("", TMPDIR, "tmpfs", MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RDONLY, "nr_inodes=2,nr_blocks=0")) { - err_perror("Failed to mount empty tmpfs for pivot_root()"); + err_perror("Failed to mount empty tmpfs for sandboxing"); return -errno; } @@ -341,13 +375,22 @@ int isolate_prefork(const struct ctx *c) } if (syscall(SYS_pivot_root, ".", ".")) { - err_perror("Failed to pivot_root() into empty tmpfs"); - return -errno; + if (c->use_chroot_fallback) { + info("Failed to pivot_root(), fallback to chroot()..."); + result = move_root(); + if (result) + return result; + } + else { + err_perror("Failed to pivot_root() into empty tmpfs"); + return -errno; + } } - - if (umount2(".", MNT_DETACH | UMOUNT_NOFOLLOW)) { - err_perror("Failed to unmount original root filesystem"); - return -errno; + else { + if (umount2(".", MNT_DETACH | UMOUNT_NOFOLLOW)) { + err_perror("Failed to unmount original root filesystem"); + return -errno; + } } /* Now that initialization is more-or-less complete, we can diff --git a/isolation.h b/isolation.h index 0576168..ea8dacb 100644 --- a/isolation.h +++ b/isolation.h @@ -12,7 +12,7 @@ void isolate_initial(int argc, char **argv); void isolate_user(uid_t uid, gid_t gid, bool use_userns, const char *userns, - enum passt_modes mode); + enum passt_modes mode, bool use_chroot_fallback); int isolate_prefork(const struct ctx *c); void isolate_postfork(const struct ctx *c); diff --git a/passt.h b/passt.h index 16506dc..2085cca 100644 --- a/passt.h +++ b/passt.h @@ -214,6 +214,7 @@ struct ip6_ctx { * @splice_only: Only enable loopback forwarding * @host_lo_to_ns_lo: Map host loopback addresses to ns loopback addresses * @freebind: Allow binding of non-local addresses for forwarding + * @use_chroot_fallback: Use chroot in case pivot_root fails * @low_wmem: Low probed net.core.wmem_max * @low_rmem: Low probed net.core.rmem_max * @no_bindtodevice: Unprivileged SO_BINDTODEVICE not available @@ -299,6 +300,7 @@ struct ctx { int splice_only; int host_lo_to_ns_lo; int freebind; + bool use_chroot_fallback; int low_wmem; int low_rmem; -- 2.43.7

2 1

[PATCH 0/3] RFC: Target address mapping
by David Gibson 01 Jul '26

01 Jul '26

Here's a next draft for target address remapping. I'm posting this as RFC because I have done minimal testing so far. I've tested the address parsing, and that we pass the existing tests, but I've done only a tiny bit of checking of the new funcionality. Posting so that it can be reviewed in parallel with that continued testing. Based on v2 of my parsing rework series. David Gibson (2): fwd_rule: Parse target adddresses for forwarding rules fwd: Clarify semantics of --host-lo-to-ns-lo Stefano Brivio (1): fwd, fwd_rule: Implement configurable target address mapping conf.c | 2 ++ fwd.c | 30 ++++++++++++++++-------------- fwd_rule.c | 31 ++++++++++++++++++++++++------- fwd_rule.h | 2 ++ passt.1 | 9 +++++---- pesto.h | 6 +++++- 6 files changed, 54 insertions(+), 26 deletions(-) -- 2.54.0

1 1

[PATCH 2/3] fwd: Clarify semantics of --host-lo-to-ns-lo
by David Gibson 01 Jul '26

01 Jul '26

The semantics of --host-lo-to-ns-lo as described in the man page don't quite make sense: It says without the option forwarded packets will appear to come _from_ the guest's public address, which is not usually true. Instead the packets will arrive *to* the guest's public address. The exact semantics are also a bit confusing in general. Rewrite both the man page and code to clarify this. The new rule is that it redirects connections addressed to a host loopback address to the same loopback address in the guest. This is notionally different from what we had in two ways: * We can now deliver to nonstandard loopback addresses within the guest, not just the default one. This is technically a behavioural change, but I think will be less surprising behaviour. * The decision is now made on the original _destination_ address, rather than source address. That's different theoreically, but not in practice, since loopback packets must have loopback addresses for both source and destination. We make it explicitly incompatible with --no-splice - previously it was allowed, but would have no effect in that case. As well as being more precise right now, these semantics will intersect better with upcoming remapping of target address by forwarding rules. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- conf.c | 2 ++ fwd.c | 22 ++++++++++------------ passt.1 | 9 +++++---- 3 files changed, 17 insertions(+), 16 deletions(-) diff --git a/conf.c b/conf.c index c4a36dee..912543fa 100644 --- a/conf.c +++ b/conf.c @@ -1792,6 +1792,8 @@ void conf(struct ctx *c, int argc, char **argv) if (c->splice_only) die("--splice-only is for pasta mode only"); } + if (c->no_splice && c->host_lo_to_ns_lo) + die("--host-lo-to-ns-lo is incompatible with --no-splice"); if (c->mode == MODE_PASTA && !c->pasta_conf_ns) { if (copy_routes_opt) diff --git a/fwd.c b/fwd.c index 042158cf..659f8d9f 100644 --- a/fwd.c +++ b/fwd.c @@ -1036,21 +1036,19 @@ uint8_t fwd_nat_from_host(const struct ctx *c, * In either case, let the kernel pick the source address to * match. */ - if (inany_v4(&ini->eaddr)) { - if (c->host_lo_to_ns_lo) - tgt->eaddr = inany_loopback4; - else - tgt->eaddr = inany_from_v4(c->ip4.addr_seen); + if (c->host_lo_to_ns_lo && inany_is_loopback(&ini->oaddr)) + tgt->eaddr = ini->oaddr; + else if (inany_v4(&ini->eaddr)) + tgt->eaddr = inany_from_v4(c->ip4.addr_seen); + else + tgt->eaddr.a6 = c->ip6.addr_seen; + + /* Let the kernel pick source address and port */ + if (inany_v4(&tgt->eaddr)) tgt->oaddr = inany_any4; - } else { - if (c->host_lo_to_ns_lo) - tgt->eaddr = inany_loopback6; - else - tgt->eaddr.a6 = c->ip6.addr_seen; + else tgt->oaddr = inany_any6; - } - /* Let the kernel pick source port */ tgt->oport = 0; if (proto == IPPROTO_UDP) /* But for UDP preserve the source port */ diff --git a/passt.1 b/passt.1 index 908fd4a4..d057aebc 100644 --- a/passt.1 +++ b/passt.1 @@ -650,10 +650,11 @@ Default is \fBauto\fR. .TP .BR \-\-host-lo-to-ns-lo -If specified, connections forwarded with \fB\-t\fR and \fB\-u\fR from -the host's loopback address will appear on the loopback address in the -guest as well. Without this option such forwarded packets will appear -to come from the guest's public address. +If specified, connections to a host loopback address forwarded with +\fB\-t\fR or \fB\-u\fR will be delivered to the same loopback address +on the guest. Without this option such connections are forwarded to +the guest's public address. This option is incompatible with +\fB--no-splice\fR. .TP .BR \-\-userns " " \fIspec -- 2.54.0

1 0

[PATCH v2 03/13] parse: Start splitting out parsing helpers
by David Gibson 01 Jul '26

01 Jul '26

As we add more complexity to what forwarding rules are allowed, our existing ad-hoc C parsing is starting to become quite awkward. We already have some parts that resemble a very simple recursive[0] descent parser, with composable subfunctions that consume as much input as they need, rather than pre-splitting based on known delimiters. Start extending this approach, by creating parse.[ch] with parsing helpers with a uniform interface. Initially we start with very simple cases: the parse_keyword() function from fwd_rule.c and another helper to check that we've reached the end of input. Rename parse_keyword() to parse_literal(), because it's not just useful for "keywords" as such. We can use it in a bunch of additional places for parsing delimiters and other symbols. This doesn't gain us a lot now but will make things clearer as we use more such parser helpers. [0] Except that the grammars we have aren't actually recursive, so neither is the code. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- Makefile | 17 ++++++++------ conf.c | 5 +++- fwd_rule.c | 33 +++++--------------------- parse.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ parse.h | 14 +++++++++++ 5 files changed, 102 insertions(+), 35 deletions(-) create mode 100644 parse.c create mode 100644 parse.h diff --git a/Makefile b/Makefile index 5ed0f702..bd729c75 100644 --- a/Makefile +++ b/Makefile @@ -36,12 +36,13 @@ BASE_CFLAGS += -pedantic -Wall -Wextra -Wno-format-zero-length -Wformat-security PASST_SRCS = arch.c arp.c bitmap.c checksum.c conf.c dhcp.c dhcpv6.c \ epoll_ctl.c flow.c fwd.c fwd_rule.c icmp.c igmp.c inany.c iov.c ip.c \ isolation.c lineread.c log.c mld.c ndp.c netlink.c migrate.c packet.c \ - passt.c pasta.c pcap.c pif.c repair.c serialise.c tap.c tcp.c \ + parse.c passt.c pasta.c pcap.c pif.c repair.c serialise.c tap.c tcp.c \ tcp_buf.c tcp_splice.c tcp_vu.c udp.c udp_flow.c udp_vu.c util.c \ vhost_user.c virtio.c vu_common.c QRAP_SRCS = qrap.c PASST_REPAIR_SRCS = passt-repair.c -PESTO_SRCS = pesto.c bitmap.c fwd_rule.c inany.c ip.c lineread.c serialise.c +PESTO_SRCS = pesto.c bitmap.c fwd_rule.c inany.c ip.c lineread.c parse.c \ + serialise.c SRCS = $(PASST_SRCS) $(QRAP_SRCS) $(PASST_REPAIR_SRCS) $(PESTO_SRCS) MANPAGES = passt.1 pasta.1 pesto.1 qrap.1 passt-repair.1 @@ -49,13 +50,14 @@ MANPAGES = passt.1 pasta.1 pesto.1 qrap.1 passt-repair.1 PASST_HEADERS = arch.h arp.h bitmap.h checksum.h conf.h dhcp.h dhcpv6.h \ epoll_ctl.h flow.h fwd.h fwd_rule.h flow_table.h icmp.h icmp_flow.h \ inany.h iov.h ip.h isolation.h lineread.h log.h migrate.h ndp.h \ - netlink.h packet.h passt.h pasta.h pcap.h pif.h repair.h serialise.h \ - siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h tcp_splice.h \ - tcp_vu.h udp.h udp_flow.h udp_internal.h udp_vu.h util.h vhost_user.h \ - virtio.h vu_common.h + netlink.h packet.h parse.h passt.h pasta.h pcap.h pif.h repair.h \ + serialise.h siphash.h tap.h tcp.h tcp_buf.h tcp_conn.h tcp_internal.h \ + tcp_splice.h tcp_vu.h udp.h udp_flow.h udp_internal.h udp_vu.h util.h \ + vhost_user.h virtio.h vu_common.h QRAP_HEADERS = arp.h ip.h passt.h util.h PASST_REPAIR_HEADERS = linux_dep.h -PESTO_HEADERS = bitmap.h common.h fwd_rule.h inany.h ip.h log.h pesto.h serialise.h +PESTO_HEADERS = bitmap.h common.h fwd_rule.h inany.h ip.h log.h parse.h \ + pesto.h serialise.h C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);} ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0) @@ -223,6 +225,7 @@ pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:bitmap.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:inany.h pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:inany.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:ip.h +pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:parse.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=unusedFunction:serialise.c pesto.cppcheck: CPPCHECK_FLAGS += --suppress=staticFunction:fwd_rule.c pesto.cppcheck: $(PESTO_SRCS) $(PESTO_HEADERS) seccomp_pesto.h diff --git a/conf.c b/conf.c index 6ab8efec..ca6c859c 100644 --- a/conf.c +++ b/conf.c @@ -52,6 +52,7 @@ #include "conf.h" #include "pesto.h" #include "serialise.h" +#include "parse.h" #define NETNS_RUN_DIR "/run/netns" @@ -1028,7 +1029,9 @@ static void conf_ugid(char *runas, uid_t *uid, gid_t *gid) static void conf_nat(const char *arg, struct in_addr *addr4, struct in6_addr *addr6, int *no_map_gw) { - if (strcmp(arg, "none") == 0) { + const char *p = arg; + + if (parse_literal(&p, "none") && parse_eoi(p)) { *addr4 = in4addr_any; *addr6 = in6addr_any; if (no_map_gw) diff --git a/fwd_rule.c b/fwd_rule.c index 04a0101d..d0e90402 100644 --- a/fwd_rule.c +++ b/fwd_rule.c @@ -24,6 +24,7 @@ #include "fwd_rule.h" #include "lineread.h" #include "log.h" +#include "parse.h" #include "serialise.h" /* Ephemeral port range: values from RFC 6335 */ @@ -427,28 +428,6 @@ static int parse_port_range(const char *s, const char **endptr, return 0; } -/** - * parse_keyword() - Parse a literal keyword - * @s: String to parse - * @endptr: Update to the character after the keyword - * @kw: Keyword to accept - * - * Return: 0, if @s starts with @kw, -EINVAL if it does not - */ -static int parse_keyword(const char *s, const char **endptr, const char *kw) -{ - size_t len = strlen(kw); - - if (strlen(s) < len) - return -EINVAL; - - if (memcmp(s, kw, len)) - return -EINVAL; - - *endptr = s + len; - return 0; -} - /** * fwd_rule_range_except() - Set up forwarding for a range of ports minus a * bitmap of exclusions @@ -568,7 +547,7 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto, continue; } - if (parse_keyword(p, &p, "auto") == 0) { + if (parse_literal(&p, "auto")) { if (p != ep) /* Garbage after the keyword */ goto bad; @@ -582,9 +561,8 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto, } /* Should be an exclude range */ - if (*p != '~') + if (!parse_literal(&p, "~")) goto bad; - p++; if (parse_port_range(p, &p, &xrange)) goto bad; @@ -616,8 +594,9 @@ static void fwd_rule_parse_ports(struct fwd_table *fwd, bool del, uint8_t proto, if (parse_port_range(p, &p, &orig_range)) goto bad; - if (*p == ':') { /* There's a range to map to as well */ - if (parse_port_range(p + 1, &p, &mapped_range)) + if (parse_literal(&p, ":")) { + /* There's a range to map to as well */ + if (parse_port_range(p, &p, &mapped_range)) goto bad; if ((mapped_range.last - mapped_range.first) != (orig_range.last - orig_range.first)) diff --git a/parse.c b/parse.c new file mode 100644 index 00000000..4e3b527d --- /dev/null +++ b/parse.c @@ -0,0 +1,68 @@ +// SPDX-License-Identifier: GPL-2.0-or-later + +/* PASST - Plug A Simple Socket Transport + * for qemu/UNIX domain socket mode + * + * PASTA - Pack A Subtle Tap Abstraction + * for network namespace/tap device mode + * + * parse.c - Composable parsing helpers + * + * Copyright Red Hat + * Author: David Gibson <david(a)gibson.dropbear.id.au> + */ + +#include <assert.h> +#include <stddef.h> +#include <fcntl.h> +#include <string.h> +#include <stdbool.h> +#include <unistd.h> + +#include "common.h" + +/** + * DOC: Theory of Operation + * + * These are a number of primitives which can be combined into parsers for + * moderately complex input. For simpler composability, they have common + * conventions. + * + * - Functions return a bool indicating whether they successfully parsed. + * - Any specific output from the parse is as output parameters + * - First argument is always @cursor, a const char **. + * - On entry, *@cursor has the point to start parsing. + * - On successful exit, *@cursor is updated to the next character after the + * parsed portion of the input + * - On failure, *@cursor and any output arguments are not modified + * + * For brevity the common parameters and return information are omitted from the + * individual function documentation comments. + */ + +/** + * parse_literal() - Parse a specified literal string + * @cursor: Point to parse from, updated on success + * @lit: Keyword to accept + */ +bool parse_literal(const char **cursor, const char *lit) +{ + size_t len = strlen(lit); + + if (strlen(*cursor) < len || memcmp(*cursor, lit, len)) + return false; + + *cursor += len; + return true; +} + +/** + * parse_eoi() - Parse end of input + * @cursor: Point to parse from + * + * Return: true if @p is at End of Input (\0), false otherwise + */ +bool parse_eoi(const char *cursor) +{ + return !(*cursor); +} diff --git a/parse.h b/parse.h new file mode 100644 index 00000000..eb51a469 --- /dev/null +++ b/parse.h @@ -0,0 +1,14 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later + * Copyright Red Hat + * Author: David Gibson <david(a)gibson.dropbear.id.au> + */ + +#ifndef PARSE_H +#define PARSE_H + +#include <stdbool.h> + +bool parse_literal(const char **cursor, const char *lit); +bool parse_eoi(const char *cursor); + +#endif /* _PARSE_H */ -- 2.54.0

1 0

[PATCH 00/12] Rework option parsing in preparation for destination remapping
by David Gibson 01 Jul '26

01 Jul '26

This was... a bit of a nightmare. It took way too long and went down a bunch of blind alleys. I'm not sure how much I like the final result: it's pleasingly terse in some cases, but in others it feels dangerously subtle, requiring a pretty careful understanding of the sequencing rules of C's &&, || and , operators. That said, while I was at many points ready to pack it in and hack my around the problems limiting the parsing for destination remapping, I couldn't really think of feasible way to do that either. So, here we are. David Gibson (12): Makefile: Add missing PESTO_HEADERS variable conf: Use parameter instead of global in conf_nat() parse: Start splitting out parsing helpers conf: Remove duplicate parsing of -F option conf: Clean up conf_ip4_prefix() parse: Add helper to parse unsigned integer values parse: Move parse_port_range() to new parsing framework parse: Add helpers for parsing IP addresses conf: Move address configuration into helper function conf: Use new parsing tools to handle -a option fwd_rule: Allow "all" port specs to be combined with other options fwd_rule: Rewrite forward rule parsing using parse.c helpers Makefile | 22 +-- common.h | 3 + conf.c | 209 ++++++++++++++++------------ conf.h | 1 + fwd_rule.c | 392 +++++++++++++++++++++++------------------------------ fwd_rule.h | 2 - inany.c | 70 +--------- inany.h | 3 - parse.c | 243 +++++++++++++++++++++++++++++++++ parse.h | 37 +++++ util.c | 12 +- 11 files changed, 591 insertions(+), 403 deletions(-) create mode 100644 parse.c create mode 100644 parse.h -- 2.54.0

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