Re: [PATCH v3 00/20] Draft, incomplete series introducing state migration

[David Gibson <david@gibson.dropbear.id.au>]

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On Sat, Feb 01, 2025 at 08:45:18AM +0100, Stefano Brivio wrote:
> On Fri, 31 Jan 2025 20:39:33 +0100
> Stefano Brivio <sbrivio@redhat.com> wrote:
> 
> > What clearly needs changes:
> 
> Maybe something less elegant but actually functional like:
> 
> ---
> static int migrate_data_v1(int fd, struct ctx *c, bool target)
> {
> 	struct iovec context[] { /* All these need to be network endian */
> 		c->hash_secret,		sizeof(c->hash_secret),
> 		c->ipv4.addr_seen,	sizeof(c->ipv4.addr_seen),
> 		c->ipv6.addr_seen,	sizeof(c->ipv6.addr_seen),
> 		c->ipv6.addr_ll_seen,	sizeof(c->ipv6.addr_ll_seen),
> 		/* Leave NDP's next_ra alone, start from 0 */
> 		&log_written /* Drop static */ sizeof(log_written),
> 	};
> 	int rc;
> 
> 	if (target)
> 		rc = read_remainder(fd, context, ARRAY_SIZE(context), 0);
> 	else
> 		rc = write_remainder(fd, context, ARRAY_SIZE(context), 0);
> 
> 	if (rc)
> 		return errno;
> 
> 	if (target)
> 		return flow_migrate_data_target_v1(fd, c);
> 	return flow_migrate_data_source_v1(fd, c);
> }
> ---
> 
> and:
> 
> ---
> struct tcp_flow_transfer_v1 {
> 	struct flow_common f;
> 
> 	uint8_t retrans;
> 
> 	uint16_t ws_from_tap; /* All BE */
> 	uint16_t ws_to_tap;
> 	uint16_t tap_mss;
> 
> 	...
> } __attribute__((packed));
> 
> union flow_transfer_v1 {
> 	struct tcp_flow_transfer_v1 tcp;
> 	...
> };
> 
> int flow_migrate_data_source_v1(int fd, struct ctx *c)
> {
> 	for_each_active_flow(flowtab) {
> 		union flow_transfer_v1 d;
> 
> 		switch (flow->f.type) {
> 		case FLOW_TCP:
> 			d.tcp.f = flow->f;
> 			d.tcp.retrans = flow->tcp.retrans;
> 			d.tcp.ws_from_tap = htons(d.tcp.ws_from_tap);
> 			...;
> 
> 			/* Fetch window stuff, socket must be in repair mode */
> 
> 		send(...);
> 	}
> 
> int flow_migrate_data_target_v1(int fd, struct ctx *c)
> {
> 	...
> }
> 
> And I'm not sure about "[PATCH 0/2] Fancier version handling for
> migration": perhaps we could switch to something radically easier
> from the beginning. I mean, as we have to drop the declarative
> approach altogether, at least let's minimise LoCs...

Yeah, I think I have a better idea that kind of covers both of these.
Patches shortly, I hope.

-- 
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

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