[PATCH iproute2] ss: small optim in tcp_show_info()

[PATCH iproute2] ss: small optim in tcp_show_info()

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Kernel can give us smaller tcp_info than our.

We copy the kernel provided structure and fill with 0
the remaining part.

Lets clear only the missing part to save some cycles, as we intend to
slightly increase tcp_info size in the future.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
diff --git a/misc/ss.c b/misc/ss.c
index 46dbb39..68961fc 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -1893,8 +1893,8 @@ static void tcp_show_info(const struct nlmsghdr *nlh, struct inet_diag_msg *r,
 		/* workaround for older kernels with less fields */
 		if (len < sizeof(*info)) {
 			info = alloca(sizeof(*info));
-			memset(info, 0, sizeof(*info));
 			memcpy(info, RTA_DATA(tb[INET_DIAG_INFO]), len);
+			memset((char *)info + len, 0, sizeof(*info) - len);
 		} else
 			info = RTA_DATA(tb[INET_DIAG_INFO]);
 

Re: [PATCH iproute2] ss: small optim in tcp_show_info()

[Stephen Hemminger]

On Wed, 06 May 2015 11:33:23 -0700
Eric Dumazet <eric.dumazet@gmail.com> wrote:

> From: Eric Dumazet <edumazet@google.com>
> 
> Kernel can give us smaller tcp_info than our.
> 
> We copy the kernel provided structure and fill with 0
> the remaining part.
> 
> Lets clear only the missing part to save some cycles, as we intend to
> slightly increase tcp_info size in the future.
> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Applied, I don't think other people will have enough sockets to notice the difference :-)