Re: [PATCH v7 17/18] conf, fwd: Allow switching to new rules received from pesto

On Tue, 5 May 2026 11:08:27 +0200 Laurent Vivier wrote:

On 5/5/26 01:11, Stefano Brivio wrote:

...

From: David Gibson

We can now receive updates to the forwarding rules from the pesto client and store them in a "pending" copy of the forwarding tables. Implement switching to using the new rules.

The logic is in a new fwd_listen_switch(). For now this closes all listening sockets related to the old tables, swaps the active and pending tables, then listens based on the new tables. In future we look to improve this so that we don't temporarily stop listening on ports that both the old and new tables specify.

Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- conf.c | 5 ++--- fwd.c | 34 ++++++++++++++++++++++++++++++++++ fwd.h | 1 + 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/conf.c b/conf.c index f035fd3..75b8291 100644 --- a/conf.c +++ b/conf.c @@ -2159,15 +2159,14 @@ void conf_handler(struct ctx *c, uint32_t events) fwd_rules_dump(info, fwd->rules, fwd->count, " ", ""); } + + fwd_listen_switch(c); }

if (events & EPOLLHUP) { debug("Configuration client hangup"); - goto close; }

- return; - close: conf_close(c);

diff --git a/fwd.c b/fwd.c index d93d2e5..35b9e2b 100644 --- a/fwd.c +++ b/fwd.c @@ -534,6 +534,40 @@ int fwd_listen_init(const struct ctx *c) return 0; }

+/** + * fwd_listen_switch() - Switch from current to pending rules table + * @c: Execution context + */ +void fwd_listen_switch(struct ctx *c) +{ + struct fwd_table *tmp[PIF_NUM_TYPES]; + unsigned i; + + /* Stop listening on the old tables */ + for (i = 0; i < PIF_NUM_TYPES; i++) { + struct fwd_table *fwd = c->fwd[i]; + + if (!fwd) + continue; + + debug("Flushing %u old %s rules", fwd->count, pif_name(i)); + fwd_listen_close(fwd); + fwd->count = fwd->sock_count = 0;

Perhaps we can reset fwd->count and fwd->sock_count in fwd_listen_close() as after fwd_listen_close() these values are wrong?

...

+ } + + /* Swap active and pending tables */ + static_assert(sizeof(tmp) == sizeof(c->fwd) && + sizeof(tmp) == sizeof(c->fwd_pending), + "Temporary has wrong size"); + memcpy(&tmp, (void *)c->fwd, sizeof(tmp)); + memcpy((void *)c->fwd, (void *)c->fwd_pending, sizeof(tmp)); + memcpy((void *)c->fwd_pending, &tmp, sizeof(tmp));

I know we have the static_assert(), but with memcpy() we usually use the sizeof() of the destination to avoid write overflow.

Changed in v8. -- Stefano