Re: [PATCH v2 7/8] tcp: make tcp_rst_no_conn() respond with correct mac address

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 12 Jun 2025 00:21:51 -0400
Jon Maloy <jmaloy@redhat.com> wrote:

> tcp_rst_no_conn() needs to identify and specify which source mac
> address to use when sending an RST to the guest. This is because
> it doesn't have access to any flow structure where this address
> could be fetched.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
>  tcp.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/tcp.c b/tcp.c
> index 1a32424..b49f603 100644
> --- a/tcp.c
> +++ b/tcp.c
> @@ -309,6 +309,7 @@
>  #include "tcp_internal.h"
>  #include "tcp_buf.h"
>  #include "tcp_vu.h"
> +#include "netlink.h"
>  
>  #ifndef __USE_MISC
>  /* From Linux UAPI, missing in netinet/tcp.h provided by musl */
> @@ -1888,6 +1889,9 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
>  			    const struct tcphdr *th, size_t l4len)
>  {
>  	struct iov_tail payload = IOV_TAIL(NULL, 0, 0);
> +	unsigned char src_mac[ETH_ALEN];
> +	union inany_addr translated;
> +	union inany_addr dst;

Same comment as previous patches, here, and...

>  	struct tcphdr *rsth;
>  	char buf[USHRT_MAX];
>  	uint32_t psum = 0;
> @@ -1897,8 +1901,15 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
>  	if (th->rst)
>  		return;
>  
> +	/* If remote host on local network - respond with its mac address */
> +	memcpy(src_mac, c->our_tap_mac, ETH_ALEN);
> +	inany_from_af(&dst, af, daddr);
> +	nat_outbound(c, &dst, &translated);
> +	if (!memcmp(&dst, &translated, sizeof(dst)))
> +		nl_mac_get(nl_sock, &dst, src_mac);

here. The rest of the series looks good to me!

-- 
Stefano