This means switching the maximum from 8 to 64 for the number of subflows and accepted ADD_ADDR. The previous limit of 8 subflows makes sense in most cases. Using more subflows will very likely *not* improve the situation, and could even decrease the performances. But there are no technical limitations nor performance impact to raise this limit, so let's do it: this will allow people with very specific use-cases, and researchers to easily create more subflows, and measure the performance impact by themselves. The theoretical limit is 255 -- the ID is written in a u8 on the wire -- but 64 is more than enough. With so many subflows, it will be costly to iterate over all of them when operations are done in bottom half. Note that the in-kernel PM will continue to create subflows in reply to ADD_ADDR with a single batch of maximum 8 subflows. Same when adding new "subflow" endpoints with the fullmesh flag. Increasing those batch limits would have a memory impact, and it looks fine not to cover these cases with larger batches for the moment. If more is needed later, the position of the last subflow from the list could be remembered, and the list iteration could continue later. Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/434 Reviewed-by: Mat Martineau Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/pm_kernel.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c index f8987a33bed4..aabd73d15c15 100644 --- a/net/mptcp/pm_kernel.c +++ b/net/mptcp/pm_kernel.c @@ -30,6 +30,7 @@ struct pm_nl_pernet { }; #define MPTCP_PM_ADDR_MAX 8 +#define MPTCP_PM_SUBFLOWS_MAX 64 static struct pm_nl_pernet *pm_nl_get_pernet(const struct net *net) { @@ -1381,10 +1382,10 @@ static int parse_limit(struct genl_info *info, int id, unsigned int *limit) return 0; *limit = nla_get_u32(attr); - if (*limit > MPTCP_PM_ADDR_MAX) { + if (*limit > MPTCP_PM_SUBFLOWS_MAX) { NL_SET_ERR_MSG_ATTR_FMT(info->extack, attr, "limit greater than maximum (%u)", - MPTCP_PM_ADDR_MAX); + MPTCP_PM_SUBFLOWS_MAX); return -EINVAL; } return 0; -- 2.53.0