[PATCH v4 17/17] conf, fwd: Allow switching to new rules received from pesto

David Gibson
2026-04-21T04:42:28Z

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 <david@gibson.dropbear.id.au>
---
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 3040a53c..6413602a 100644
--- a/conf.c
+++ b/conf.c
@@ -2133,15 +2133,14 @@ 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 d93d2e5d..35b9e2b0 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;
+ }
+
+ /* 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));
+
+ /* Start listening on the new tables */
+ if (fwd_listen_init(c) < 0)
+ err("Error switching to new forwarding rules");
+}
+
/* 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 ac247826..b60697d9 100644
--- a/fwd.h
+++ b/fwd.h
@@ -61,6 +61,7 @@ int fwd_listen_sync(const struct ctx *c, uint8_t pif,
const struct fwd_scan *tcp, const struct fwd_scan *udp);
void fwd_listen_close(const struct fwd_table *fwd);
int fwd_listen_init(const struct ctx *c);
+void fwd_listen_switch(struct ctx *c);

bool nat_inbound(const struct ctx *c, const union inany_addr *addr,
union inany_addr *translated);
--
2.53.0