- dev - passt

[PATCH 0/1] Leftover parsing patch
by David Gibson 08 Sep '26

08 Sep '26

I'm not sure if this patch is particularly useful, however it was already complete, left over from the earlier parsing rework. So, I thought I might as well post it in case it's interesting. David Gibson (1): parse: Convert parse_mac() to conventions of parse.c Makefile | 1 + conf.c | 43 ++++++++----------------------------------- parse.c | 30 ++++++++++++++++++++++++++++++ parse.h | 1 + 4 files changed, 40 insertions(+), 35 deletions(-) -- 2.55.0

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[PATCH] netlink: Don't warn about multiple interfaces when there's only one
by Hayato Kiwata 01 Sep '26

01 Sep '26

Suppose there is a single network interface on the host, with two addresses of different prefixes assigned to it. In this situation, running pasta to create an isolated netns prints "Multiple interfaces with %s routes, picked first", even though there is in fact only one candidate interface. Reproducer: sudo ip link add dummy42 type dummy sudo ip link set dev dummy42 up sudo ip addr add fdaa:aaaa:aaaa::1/64 dev dummy42 sudo ip addr add fdbb:bbbb:bbbb::1/64 dev dummy42 pasta --config-net -- true This message is meant to indicate that there are multiple candidate interfaces, but in fact there is only one, which can mislead users. Therefore, avoid printing this message when there are multiple non-default routes that all belong to the same interface. Fixes: 450a6131beab ("netlink: With no default route, pick the first interface with a route") Signed-off-by: Hayato Kiwata <dev(a)haytok.jp> --- netlink.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/netlink.c b/netlink.c index 8d20dbb..225b666 100644 --- a/netlink.c +++ b/netlink.c @@ -271,6 +271,7 @@ unsigned int nl_get_ext_if(int s, sa_family_t af) }; unsigned defifi = 0, anyifi = 0; unsigned ndef = 0, nany = 0; + bool multi_anyif = false; struct nlmsghdr *nh; struct rtattr *rta; char buf[NLBUFSIZ]; @@ -330,6 +331,8 @@ unsigned int nl_get_ext_if(int s, sa_family_t af) nany++; if (!anyifi) anyifi = thisifi; + else if (anyifi != thisifi) + multi_anyif = true; } } @@ -345,7 +348,7 @@ unsigned int nl_get_ext_if(int s, sa_family_t af) } if (anyifi) { - if (nany > 1) { + if (multi_anyif) { info("Multiple interfaces with %s routes, picked first", af_name(af)); } -- 2.39.5 (Apple Git-154)

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[PATCH 3/5] util: Add missing O_CLOEXEC for !HAS_GETRANDOM path
by David Gibson 21 Aug '26

21 Aug '26

It rarely matters, since we usually have getrandom(), but in case we don't our open() of /dev/random was missing O_CLOEXEC, which can cause clang warnings. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/util.c b/util.c index 500e8f55..df972a05 100644 --- a/util.c +++ b/util.c @@ -964,7 +964,7 @@ void raw_random(void *buf, size_t buflen) { size_t random_read = 0; #ifndef HAS_GETRANDOM - int fd = open(DEV_RANDOM, O_RDONLY); + int fd = open(DEV_RANDOM, O_RDONLY | O_CLOEXEC); if (fd < 0) die_perror("Couldn't open %s", DEV_RANDOM); -- 2.53.0

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[PATCH 2/5] util: Eliminate a stray trailing whitespace
by David Gibson 21 Aug '26

21 Aug '26

We generally avoid trailing whitespace, but one slipped in. Fix it. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/util.c b/util.c index 28c32e43..500e8f55 100644 --- a/util.c +++ b/util.c @@ -1072,7 +1072,7 @@ void passt_exit(int status) /* Make sure we don't leave any messages incomplete */ (void)fflush(stderr); (void)fflush(stdout); - + _exit(status); } -- 2.53.0

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[PATCH 0/5] Add AFL++ fuzzing support for passt
by Anshu Kumari 18 Aug '26

18 Aug '26

This series adds integrated AFL++ fuzzing support for passt, extending the earlier work by AbdAlRahman Gad with persistent mode, bidirectional protocol fuzzing, and real TCP connection coverage via a companion test server. Architecture ------------ The fuzzer runs passt in AFL++ persistent mode (__AFL_LOOP) with shared memory fuzzing. A separate test server process connects to passt's UNIX socket and listens on 127.0.0.1:9999 for real TCP connections: Deterministic wrappers replace clock_gettime, getrandom, getsockopt, and recv-family calls to eliminate kernel-level non-determinism. Per-iteration reset of the flow table, epoll instance, and clock. *** BLURB HERE *** Anshu Kumari (5): fuzz: Add deterministic wrappers for system calls fuzz: Add flow type guards for fuzzing stability fuzz: Bypass isolation and adapt sockets for AFL++ fuzz: Add AFL++ persistent mode fuzz loop fuzz: Add test server for bidirectional protocol fuzzing Makefile | 28 +- fuzz-server.c | 490 +++++++++++++++++++++++++++++++++ fuzz.c | 275 ++++++++++++++++++ fuzz.h | 62 +++++ fuzzing/README.fuzzing.md | 95 +++++++ fuzzing/testcase_dir/empty.bin | Bin 0 -> 12 bytes icmp.c | 14 +- isolation.c | 11 + passt.c | 189 +++++++++++++ passt.h | 4 + tap.c | 21 ++ tcp.c | 19 +- tcp_buf.c | 1 + tcp_splice.c | 10 + udp.c | 29 +- udp_flow.c | 5 + util.c | 10 + 17 files changed, 1251 insertions(+), 12 deletions(-) create mode 100644 fuzz-server.c create mode 100644 fuzz.c create mode 100644 fuzz.h create mode 100644 fuzzing/README.fuzzing.md create mode 100644 fuzzing/testcase_dir/empty.bin -- 2.55.0

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[PATCH 0/2] Allow users to give source address with --gateway also for IPv6
by Stefano Brivio 18 Aug '26

18 Aug '26

...just like it happens with IPv4. This offers a solution for https://bugs.passt.top/show_bug.cgi?id=217, as Podman can specify --address and --gateway for IPv6 local mode, and provide a unique local address, without the need to introduce other options. Further options might be more appropriate, strictly speaking, but as the future perspective is to eventually generalise NAT tables, it would be nice to avoid them right now. Stefano Brivio (2): conf: Honour --address, --gateway, --netmask in local mode as well conf, fwd: Prefer same-scope address as inbound source address from host conf.c | 23 +++++++++++++++++++---- fwd.c | 6 +++++- passt.h | 2 ++ 3 files changed, 26 insertions(+), 5 deletions(-) -- 2.43.0

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[RFC v3 0/8] Add vhost-net kernel support to pasta
by Ammar Yasser 17 Aug '26

17 Aug '26

This work is based on the original v2 RFC by Eugenio Perez, and continues its version numbering. Link: https://archives.passt.top/passt-dev/20250709174748.3514693-1-eperezma@redh… vhost-net is a kernel device that allows reading and writing packets to a tap device using virtqueues instead of read(2) and write(2) and their vectored counterparts. Frames are handed over through a shared descriptor ring, so several of them can be passed to the kernel at once rather than issuing a syscall per frame. This RFC introduces an option to pasta, --vhost, which if specified will leverage this mode of acceleration. I haven't benchmarked this against the existing path yet, so the performance argument above is so far unquantified. TODO: test what happens when the namespace wants to send data but we don't have available rx descriptors, and vice versa for tx. TODO: tap_send_frames() currently carries an implicit contract that it is synchronous: once it returns, the caller is free to reuse its frame buffers. That holds for writev() and for vhost-user, but not for vhost-kernel, where returning only means the descriptors have been queued. pasta can overwrite a buffer while the kernel vhost worker thread is still reading the descriptor pointing at it. I haven't settled on how to restore that contract, and would appreciate direction before building further on top of it. Ammar Yasser (8): tap: Move the tap_hdr file to a separate file udp,tcp: Make protocol specific buffers public conf: Add context fields, epoll types and the --vhost flag to pasta virtio: Define the pasta vhost interface virtio: Implement the pasta vhost functions virtio: Implement pasta vhost acceleration guest->pasta path pasta: Implement pasta vhost TX (pasta->guest) prerequisites tap: Implement pasta vhost TX conf.c | 6 + epoll_type.h | 4 + passt.c | 9 ++ passt.h | 17 ++- tap.c | 317 +++++++++++++++++++++++++++++++++++++++++-------- tap.h | 10 +- tap_hdr.h | 19 +++ tcp_buf.c | 51 +++++--- tcp_buf.h | 14 +++ udp.c | 68 ++++++----- udp.h | 53 +++++++++ udp_internal.h | 13 -- virtio.c | 283 ++++++++++++++++++++++++++++++++++++++++++- virtio.h | 76 ++++++++++++ 14 files changed, 827 insertions(+), 113 deletions(-) create mode 100644 tap_hdr.h -- 2.34.1

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[PATCH 0/7] multithreading: Add worker threads for queue pair processing
by Laurent Vivier 14 Aug '26

14 Aug '26

NOTE: This series has known stability issues (hangs and crashes under load) and is submitted for reference and testing purposes. This series adds pthread-based worker threads to enable parallel processing of queue pairs in vhost-user mode. Each queue pair gets its own worker thread with a dedicated epollfd. Thread 0 handles control events (listen sockets, vhost-user commands, repair, netlink) plus queue pair 0. Threads 1-15 handle only their assigned queue pair events. Threads start/stop dynamically via SET_VRING_ENABLE. Known issues include system hangs under load and crashes when virtqueues are exhausted. A temporary workaround in virtio.c masks underlying coordination problems between worker threads that need proper fixes. Based-on: 20260731162329.3552800-1-lvivier(a)redhat.com Laurent Vivier (7): vhost_user: Reset vq enable flag in vu_cleanup() threading: Add basic threading infrastructure passt: Integrate main event loop with threading infrastructure flow: Delegate epoll file descriptor management to threading subsystem ctx: Remove epollfd from context structure vhost-user: Add per-qpair worker threads virtio: Prevent crash on virtqueue exhaustion with temporary workaround Makefile | 8 +- conf.c | 10 ++- flow.c | 12 +-- flow.h | 4 +- fwd.c | 4 +- isolation.c | 6 +- netlink.c | 4 +- passt.c | 151 ++++++++++++++++++++++++-------------- passt.h | 7 +- pasta.c | 3 +- pif.c | 3 +- repair.c | 12 ++- tap.c | 9 ++- tcp.c | 3 +- tcp_splice.c | 1 + threading.c | 202 +++++++++++++++++++++++++++++++++++++++++++++++++++ threading.h | 22 ++++++ vhost_user.c | 34 +++++++-- vhost_user.h | 1 + virtio.c | 8 +- vu_common.c | 13 ++-- 21 files changed, 417 insertions(+), 100 deletions(-) create mode 100644 threading.c create mode 100644 threading.h -- 2.54.0

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Patch for the close_range() musl build failure
by Huang Jing 13 Aug '26

13 Aug '26

Please see attached patch.

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[PATCH v2 00/10] multithreading: Prepare data structures for concurrent queue pair workers
by Laurent Vivier 05 Aug '26

05 Aug '26

This series makes the passt data structures safe for concurrent access by multiple worker threads, each handling a different queue pair. It builds on the multiqueue series which threads the queue pair parameter through the network stack. The changes fall into four categories: 1. Per-queue-pair data isolation: - Convert packet pools (pool_tap4, pool_tap6) to per-queue-pair arrays - Convert L4 sequence batching arrays (tap4_l4, tap6_l4) similarly - Move flow and TCP timer state out of global/context structures into per-caller parameters 2. Stack-local buffers: - Move static iovec and virtqueue buffers onto the stack in tcp.c, tcp_vu.c, and udp_vu.c so each thread operates on its own copy 3. Locking for remaining shared state: - pthread_mutex on pre-opened socket pools (init_sock_pool4/6) - pthread_rwlock on the flow table, hash table, and free list, with read locks for lookups and write locks for mutations - _Thread_local for flow_new_entry so each thread independently tracks its in-progress allocation - Per-qpair filtering in flow_defer_handler() so each worker only processes its own flows 4. Lock-free flow migration between queue pairs: - When guest steers traffic to a different TX queue, flows migrate lazily using a to_migrate[] array - flow_migrate_mark() records target qpair from tap path (write-once, no lock needed) - flow_migrate_epollfd() completes migration on next socket/timer event by moving fd and updating qpair on the old thread - TCP timers migrate the same way using new tcp_timer_epoll_add() helper Global operations that don't need per-queue-pair handling (tcp_payload_flush, socket pool refills) are guarded to run only on queue pair 0. v2: - Rebase on latest master and multiqueue v6 - Split v1's "flow: Add mutex and per-qpair filtering..." into two patches: - "flow: Add locking, per-qpair filtering, and intermediate state handling" (locking only) - "flow: Add lazy, lock-free flow migration between queue pairs" (migration logic separated) - Changed from simple mutex to pthread_rwlock for flow table (read locks for lookups, write locks for mutations and free-list rebuild) - Updated flow_foreach() and flow_defer_handler() to handle intermediate flow states (NEW, INI, TGT, TYPED) that can be observed between flow_alloc() and FLOW_ACTIVATE() when lock is released - New patch: "tcp: Extract tcp_timer_epoll_add() helper" - factors out epoll registration for timer migration support - flow_migrate_epollfd() now uses tcp_timer_epoll_add() for timer migration v1: - Initial submission Based-on: 20260616125130.1324274-1-lvivier(a)redhat.com Laurent Vivier (10): tap: Convert packet pools to per-queue-pair arrays for multiqueue tap: Make L4 sequence pools per-qpair for thread safety tcp: Make static buffers stack-local for thread safety udp_vu: Make virtqueue buffers stack-local for thread safety flow: Make flow timer per-caller for thread safety tcp: Make TCP timer state per-caller and guard global tasks tcp: Protect init socket pools with mutex for thread safety tcp: Extract tcp_timer_epoll_add() helper flow: Add locking, per-qpair filtering, and intermediate state handling flow: Add lazy, lock-free flow migration between queue pairs flow.c | 222 ++++++++++++++++++++++++++++++++++++++++++++++----- flow.h | 5 +- flow_table.h | 2 +- icmp.c | 10 ++- passt.c | 37 +++++---- tap.c | 109 ++++++++++++++----------- tap.h | 2 +- tcp.c | 108 ++++++++++++++++++------- tcp.h | 9 +-- tcp_vu.c | 33 +++++--- udp.c | 3 + udp_flow.c | 4 + udp_vu.c | 4 +- vu_common.c | 2 +- 14 files changed, 409 insertions(+), 141 deletions(-) -- 2.54.0

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