Re: [PATCH net-next v3 1/3] ipv4: support sport, dport and ip_proto in RTM_GETROUTE

On Wed, May 16, 2018 at 11:37 AM, David Miller [off-list ref] wrote:

From: Roopa Prabhu <redacted>
Date: Tue, 15 May 2018 20:55:06 -0700

quoted

+static int inet_rtm_getroute_reply(struct sk_buff *in_skb, struct nlmsghdr *nlh,
+                                __be32 dst, __be32 src, struct flowi4 *fl4,
+                                struct rtable *rt, struct fib_result *res)
+{
+     struct net *net = sock_net(in_skb->sk);
+     struct rtmsg *rtm = nlmsg_data(nlh);
+     u32 table_id = RT_TABLE_MAIN;
+     struct sk_buff *skb;
+     int err = 0;
+
+     skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
+     if (!skb)
+             return -ENOMEM;

If the caller can use GFP_KERNEL, so can this allocation.

yes, but we hold rcu read lock before calling the reply function for fib result.
I did consider allocating the skb before the read lock..but then the
refactoring (into a separate netlink reply func) would seem
unnecessary.

I am fine with pre-allocating and undoing the refactoring if that works better.