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Message-ID: <4F8EDF99.2040401@katalix.com>
Date: Wed, 18 Apr 2012 16:36:57 +0100
From: James Chapman <jchapman@...alix.com>
To: Benjamin LaHaise <bcrl@...ck.org>
CC: davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH 4/4] net/l2tp: add support for L2TP over IPv6 UDP encap
On 18/04/12 14:44, Benjamin LaHaise wrote:
> Now that encap_rcv() works on IPv6 UDP sockets, wire L2TP up to IPv6.
> Support has been tested with and without hardware offloading.
>
> Signed-off-by: Benjamin LaHaise <bcrl@...ck.org>
...
> diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
> index f6732b6..8cd5f4b 100644
> --- a/net/l2tp/l2tp_core.c
> +++ b/net/l2tp/l2tp_core.c
> @@ -53,6 +53,9 @@
> #include <net/inet_common.h>
> #include <net/xfrm.h>
> #include <net/protocol.h>
> +#include <net/inet6_connection_sock.h>
> +#include <net/inet_ecn.h>
> +#include <net/ip6_route.h>
>
> #include <asm/byteorder.h>
> #include <linux/atomic.h>
> @@ -446,21 +449,43 @@ static inline int l2tp_verify_udp_checksum(struct sock *sk,
> {
> struct udphdr *uh = udp_hdr(skb);
> u16 ulen = ntohs(uh->len);
> - struct inet_sock *inet;
> __wsum psum;
>
> - if (sk->sk_no_check || skb_csum_unnecessary(skb) || !uh->check)
> - return 0;
> -
> - inet = inet_sk(sk);
> - psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr, ulen,
> - IPPROTO_UDP, 0);
> -
> - if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
> - !csum_fold(csum_add(psum, skb->csum)))
> + if (sk->sk_no_check || skb_csum_unnecessary(skb))
> return 0;
>
> - skb->csum = psum;
> +#if IS_ENABLED(CONFIG_IPV6)
> + if (sk->sk_family == PF_INET6) {
> + if (!uh->check) {
> + LIMIT_NETDEBUG(KERN_INFO "L2TP: IPv6: checksum is 0\n");
> + return 1;
> + }
> + if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
> + !csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> + &ipv6_hdr(skb)->daddr, ulen,
> + IPPROTO_UDP, skb->csum)) {
> + skb->ip_summed = CHECKSUM_UNNECESSARY;
> + return 0;
> + }
> + skb->csum = ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> + &ipv6_hdr(skb)->daddr,
> + skb->len, IPPROTO_UDP,
> + 0));
> + } else
> +#endif
> + {
> + struct inet_sock *inet;
> + if (!uh->check)
> + return 0;
> + inet = inet_sk(sk);
> + psum = csum_tcpudp_nofold(inet->inet_saddr, inet->inet_daddr,
> + ulen, IPPROTO_UDP, 0);
> +
> + if ((skb->ip_summed == CHECKSUM_COMPLETE) &&
> + !csum_fold(csum_add(psum, skb->csum)))
> + return 0;
> + skb->csum = psum;
> + }
>
> return __skb_checksum_complete(skb);
> }
I'm seeing UDP checksum errors with a loopback test. Regular
(non-loopback) sessions and loopback ipv4 sessions are fine. I retested
your previous patch and verified that it has the same problem. Although
loopback is a weird config, does it indicate a possible problem? Here is
the debug trace:
[ 223.260340] lo: hw csum failure
[ 223.260718] Pid: 1146, comm: pppd Not tainted 3.4.0-rc2+ #5
[ 223.261373] Call Trace:
[ 223.261840] [<c1247b55>] netdev_rx_csum_fault+0x29/0x30
[ 223.262467] [<c12430ac>] __skb_checksum_complete_head+0x42/0x57
[ 223.263159] [<d8a41230>] l2tp_udp_encap_recv+0x13a/0x413 [l2tp_core]
[ 223.263892] [<d8a78c46>] ? pppol2tp_recv+0x11e/0x11e [l2tp_ppp]
[ 223.265741] [<c12cb69f>] ? rcu_read_unlock+0x4d/0x4f
[ 223.266902] [<c12c0028>] ? addrconf_notify+0x5c4/0x7e2
[ 223.268066] [<c12cd2d6>] udpv6_queue_rcv_skb+0x4a/0x256
[ 223.269176] [<c12cd9c6>] __udp6_lib_rcv+0x2c8/0x400
[ 223.269733] [<c12cdb10>] udpv6_rcv+0x12/0x16
[ 223.270222] [<c12bb1d3>] ip6_input_finish+0x1be/0x346
[ 223.270793] [<c12bb015>] ? T.1206+0x4d/0x4d
[ 223.271270] [<c12bb393>] T.1207+0x38/0x3f
[ 223.271729] [<c12bafa1>] ? rcu_read_unlock+0x4f/0x4f
[ 223.272334] [<c12bb79e>] ip6_input+0x17/0x19
[ 223.272824] [<c12bb015>] ? T.1206+0x4d/0x4d
[ 223.273302] [<c12bafc5>] ip6_rcv_finish+0x24/0x27
[ 223.276246] [<c12bb393>] T.1207+0x38/0x3f
[ 223.276727] [<c12bb726>] ipv6_rcv+0x38c/0x3ed
[ 223.277242] [<c12bafa1>] ? rcu_read_unlock+0x4f/0x4f
[ 223.277833] [<c124b97b>] __netif_receive_skb+0x46c/0x4a7
[ 223.278459] [<c124ba54>] process_backlog+0x9e/0x16e
[ 223.279068] [<c124c26d>] net_rx_action+0x9d/0x1af
[ 223.279701] [<c102cadd>] __do_softirq+0xb1/0x17f
[ 223.280281] [<c102ca2c>] ? irq_enter+0x5d/0x5d
[ 223.280807] <IRQ> [<c122112d>] ? ppp_channel_push+0x62/0x93
[ 223.281489] [<c102c9a0>] ? _local_bh_enable_ip+0x8e/0xa6
[ 223.282406] [<c102c9c0>] ? local_bh_enable_ip+0x8/0xa
[ 223.283026] [<c12fe2d6>] ? _raw_spin_unlock_bh+0x25/0x28
[ 223.283655] [<c122112d>] ? ppp_channel_push+0x62/0x93
[ 223.284308] [<c1221200>] ? ppp_write+0xa2/0xac
[ 223.284855] [<c122115e>] ? ppp_channel_push+0x93/0x93
[ 223.285451] [<c10e0412>] ? vfs_write+0x80/0xde
[ 223.286059] [<c10e0d2a>] ? fget_light+0x2b/0x8f
[ 223.286593] [<c10e0507>] ? sys_write+0x3b/0x60
[ 223.287121] [<c130431f>] ? sysenter_do_call+0x12/0x38
--
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development
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