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Message-ID: <20240313133602.GA1263314@maili.marvell.com>
Date: Wed, 13 Mar 2024 19:06:02 +0530
From: Ratheesh Kannoth <rkannoth@...vell.com>
To: Mark Cilissen <mark@...suba.nl>
CC: <netdev@...r.kernel.org>, Hans de Goede <hdegoede@...hat.com>,
Eric
Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Breno Leitao
<leitao@...ian.org>, Ingo Molnar <mingo@...hat.com>,
"David S. Miller"
<davem@...emloft.net>,
Paolo Abeni <pabeni@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] netpoll: support sending over raw IP interfaces
On 2024-03-13 at 18:16:13, Mark Cilissen (mark@...suba.nl) wrote:
> Currently, netpoll only supports interfaces with an ethernet-compatible
> link layer. Certain interfaces like SLIP do not have a link layer
> on the network interface level at all and expect raw IP packets,
> and could benefit from being supported by netpoll.
>
> This commit adds support for such interfaces by using the network device's
> `hard_header_len` field as an indication that no link layer is present.
> If that is the case we simply skip adding the ethernet header, causing
> a raw IP packet to be sent over the interface. This has been confirmed
> to add netconsole support to at least SLIP and WireGuard interfaces.
>
> Signed-off-by: Mark Cilissen <mark@...suba.nl>
> ---
> Documentation/networking/netconsole.rst | 3 ++-
> net/core/netpoll.c | 30 ++++++++++++++++---------
> 2 files changed, 22 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
> index d55c2a22ec7a..434ce0366027 100644
> --- a/Documentation/networking/netconsole.rst
> +++ b/Documentation/networking/netconsole.rst
> @@ -327,4 +327,5 @@ enable the logging of even the most critical kernel bugs. It works
> from IRQ contexts as well, and does not enable interrupts while
> sending packets. Due to these unique needs, configuration cannot
> be more automatic, and some fundamental limitations will remain:
> -only IP networks, UDP packets and ethernet devices are supported.
> +only UDP packets over IP networks, over ethernet links if a
> +hardware layer is required, are supported.
> diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> index 543007f159f9..0299fb71b456 100644
> --- a/net/core/netpoll.c
> +++ b/net/core/netpoll.c
> @@ -399,7 +399,7 @@ EXPORT_SYMBOL(netpoll_send_skb);
>
> void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
> {
> - int total_len, ip_len, udp_len;
> + int total_len, ip_len, udp_len, link_len;
> struct sk_buff *skb;
> struct udphdr *udph;
> struct iphdr *iph;
> @@ -416,7 +416,10 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
> else
> ip_len = udp_len + sizeof(*iph);
>
> - total_len = ip_len + LL_RESERVED_SPACE(np->dev);
> + /* if there's a hardware header assume ethernet, else raw IP */
Taking an assumption based on dev's lower layer does not look to be good.
why not transmit packet from skb_network_header() in your driver (by making
changes in your driver)
> + eth = NULL;
> + link_len = np->dev->hard_header_len ? LL_RESERVED_SPACE(np->dev) : 0;
> + total_len = ip_len + link_len;
>
> skb = find_skb(np, total_len + np->dev->needed_tailroom,
> total_len - len);
> @@ -458,9 +461,11 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
> ip6h->saddr = np->local_ip.in6;
> ip6h->daddr = np->remote_ip.in6;
>
> - eth = skb_push(skb, ETH_HLEN);
> - skb_reset_mac_header(skb);
> - skb->protocol = eth->h_proto = htons(ETH_P_IPV6);
> + skb->protocol = htons(ETH_P_IPV6);
> + if (link_len) {
> + eth = skb_push(skb, ETH_HLEN);
> + skb_reset_mac_header(skb);
> + }
> } else {
> udph->check = 0;
> udph->check = csum_tcpudp_magic(np->local_ip.ip,
> @@ -487,13 +492,18 @@ void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
> put_unaligned(np->remote_ip.ip, &(iph->daddr));
> iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
>
> - eth = skb_push(skb, ETH_HLEN);
> - skb_reset_mac_header(skb);
> - skb->protocol = eth->h_proto = htons(ETH_P_IP);
> + skb->protocol = htons(ETH_P_IP);
> + if (link_len) {
> + eth = skb_push(skb, ETH_HLEN);
> + skb_reset_mac_header(skb);
> + }
> }
>
> - ether_addr_copy(eth->h_source, np->dev->dev_addr);
> - ether_addr_copy(eth->h_dest, np->remote_mac);
> + if (eth) {
> + eth->h_proto = skb->protocol;
> + ether_addr_copy(eth->h_source, np->dev->dev_addr);
> + ether_addr_copy(eth->h_dest, np->remote_mac);
> + }
>
> skb->dev = np->dev;
>
> --
> 2.43.0
>
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