Re: [PATCH nftables 4/4] src: mnl: retry when we hit -ENOBUFS

[Florian Westphal <fw@strlen.de>]

Pablo Neira Ayuso <pablo@netfilter.org> wrote:
> > diff --git a/src/mnl.c b/src/mnl.c
> > index 97a2e0765189..0c7a4c1fa63f 100644
> > --- a/src/mnl.c
> > +++ b/src/mnl.c
> > @@ -311,6 +311,7 @@ int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
> >  	int ret, fd = mnl_socket_get_fd(nl), portid = mnl_socket_get_portid(nl);
> >  	uint32_t iov_len = nftnl_batch_iovec_len(ctx->batch);
> >  	char rcv_buf[MNL_SOCKET_BUFFER_SIZE];
> > +	unsigned int enobuf_restarts = 0;
> >  	size_t avg_msg_size, batch_size;
> >  	const struct sockaddr_nl snl = {
> >  		.nl_family = AF_NETLINK
> > @@ -320,6 +321,7 @@ int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
> >  		.tv_usec	= 0
> >  	};
> >  	struct iovec iov[iov_len];
> > +	unsigned int scale = 4;
> >  	struct msghdr msg = {};
> >  	fd_set readfds;
> >  
> > @@ -327,9 +329,7 @@ int mnl_batch_talk(struct netlink_ctx *ctx, struct list_head *err_list,
> >  
> >  	batch_size = mnl_nft_batch_to_msg(ctx, &msg, &snl, iov, iov_len);
> >  	avg_msg_size = div_round_up(batch_size, num_cmds);
> > -
> > -	mnl_set_rcvbuffer(ctx->nft->nf_sock, num_cmds * avg_msg_size * 4);
> 
> Leaving this in place does not harm, right? This would speed up things
> for x86_64.

ok, I can keep it.

> It looks like s390 allocates larger page there to accomodate each
> netlink event.
> 
> All this probing and guess games could be fixed if there is a
> getsockopt() to fetch sk->sk_rmem_alloc, this is already exposed in
> netlink via /proc. Later :-)

How? The error occurs because sk_rmem_alloc is not large enough to
store all the netlink acks in the socket backlog.