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KRT: Scan routing tables separetely on linux to avoid congestion

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Remove compile-time sysdep option CONFIG_ALL_TABLES_AT_ONCE, replace it
with runtime ability to run either separate table scans or shared scan.

On Linux, use separate table scans by default when the netlink socket
option NETLINK_GET_STRICT_CHK is available, but retreat to shared scan
when it fails.

Running separate table scans has advantages where some routing tables are
managed independently, e.g. when multiple routing daemons are running on
the same machine, as kernel routing table modification performance is
significantly reduced when the table is modified while it is being
scanned.

Thanks Daniel Gröber for the original patch and Toke Høiland-Jørgensen
for suggestions.
This commit is contained in:
Ondrej Zajicek
2022-07-24 02:15:20 +02:00
parent 971721c9b5
commit 534d0a4b44
5 changed files with 78 additions and 49 deletions
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49
sysdep/linux/netlink.c
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@@ -161,16 +161,13 @@ nl_open_sock(struct nl_sock *nl)
}
}
static void
static int
nl_set_strict_dump(struct nl_sock *nl UNUSED, int strict UNUSED)
{
/*
* Strict checking is not necessary, it improves behavior on newer kernels.
* If it is not available (missing SOL_NETLINK compile-time, or ENOPROTOOPT
* run-time), we can just ignore it.
*/
#ifdef SOL_NETLINK
setsockopt(nl->fd, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &strict, sizeof(strict));
return setsockopt(nl->fd, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &strict, sizeof(strict));
#else
return -1;
#endif
}
@@ -198,10 +195,17 @@ nl_cfg_rx_buffer_size(struct config *cfg)
static void
nl_open(void)
{
if ((nl_scan.fd >= 0) && (nl_req.fd >= 0))
return;
nl_open_sock(&nl_scan);
nl_open_sock(&nl_req);
nl_set_strict_dump(&nl_scan, 1);
if (nl_set_strict_dump(&nl_scan, 1) < 0)
{
log(L_WARN "KRT: Netlink strict checking failed, will scan all tables at once");
krt_use_shared_scan();
}
}
static void
@@ -256,11 +260,13 @@ nl_request_dump_addr(int af)
}
static void
nl_request_dump_route(int af)
nl_request_dump_route(int af, int table_id)
{
struct {
struct nlmsghdr nh;
struct rtmsg rtm;
struct rtattr rta;
u32 table_id;
} req = {
.nh.nlmsg_type = RTM_GETROUTE,
.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)),
@@ -269,7 +275,17 @@ nl_request_dump_route(int af)
.rtm.rtm_family = af,
};
send(nl_scan.fd, &req, sizeof(req), 0);
if (table_id < 256)
req.rtm.rtm_table = table_id;
else
{
req.rta.rta_type = RTA_TABLE;
req.rta.rta_len = RTA_LENGTH(4);
req.table_id = table_id;
req.nh.nlmsg_len = NLMSG_ALIGN(req.nh.nlmsg_len) + req.rta.rta_len;
}
send(nl_scan.fd, &req, req.nh.nlmsg_len, 0);
nl_scan.last_hdr = NULL;
}
@@ -1976,18 +1992,27 @@ nl_parse_route(struct nl_parse_state *s, struct nlmsghdr *h)
}
void
krt_do_scan(struct krt_proto *p UNUSED) /* CONFIG_ALL_TABLES_AT_ONCE => p is NULL */
krt_do_scan(struct krt_proto *p)
{
struct nlmsghdr *h;
struct nl_parse_state s;
nl_parse_begin(&s, 1);
nl_request_dump_route(AF_UNSPEC);
/* Table-specific scan or shared scan */
if (p)
nl_request_dump_route(p->af, krt_table_id(p));
else
nl_request_dump_route(AF_UNSPEC, 0);
while (h = nl_get_scan())
{
if (h->nlmsg_type == RTM_NEWROUTE || h->nlmsg_type == RTM_DELROUTE)
nl_parse_route(&s, h);
else
log(L_DEBUG "nl_scan_fire: Unknown packet received (type=%d)", h->nlmsg_type);
}
nl_parse_end(&s);
}