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Date: Sat, 30 Jan 2021 15:55:24 +0000
From: Alexander Lobakin <alobakin@...me>
To: Dongseok Yi <dseok.yi@...sung.com>
Cc: Alexander Lobakin <alobakin@...me>,
"David S. Miller" <davem@...emloft.net>,
Steffen Klassert <steffen.klassert@...unet.com>,
namkyu78.kim@...sung.com, Jakub Kicinski <kuba@...nel.org>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
David Ahern <dsahern@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Willem de Bruijn <willemb@...gle.com>,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
bpf@...r.kernel.org
Subject: Re: [RESEND PATCH net v4] udp: ipv4: manipulate network header of NATed UDP GRO fraglist
From: Dongseok Yi <dseok.yi@...sung.com>
Date: Sat, 30 Jan 2021 08:13:27 +0900
> UDP/IP header of UDP GROed frag_skbs are not updated even after NAT
> forwarding. Only the header of head_skb from ip_finish_output_gso ->
> skb_gso_segment is updated but following frag_skbs are not updated.
>
> A call path skb_mac_gso_segment -> inet_gso_segment ->
> udp4_ufo_fragment -> __udp_gso_segment -> __udp_gso_segment_list
> does not try to update UDP/IP header of the segment list but copy
> only the MAC header.
>
> Update port, addr and check of each skb of the segment list in
> __udp_gso_segment_list. It covers both SNAT and DNAT.
>
> Fixes: 9fd1ff5d2ac7 (udp: Support UDP fraglist GRO/GSO.)
> Signed-off-by: Dongseok Yi <dseok.yi@...sung.com>
> Acked-by: Steffen Klassert <steffen.klassert@...unet.com>
> ---
> v1:
> Steffen Klassert said, there could be 2 options.
> https://lore.kernel.org/patchwork/patch/1362257/
> I was trying to write a quick fix, but it was not easy to forward
> segmented list. Currently, assuming DNAT only.
>
> v2:
> Per Steffen Klassert request, moved the procedure from
> udp4_ufo_fragment to __udp_gso_segment_list and support SNAT.
>
> v3:
> Per Steffen Klassert request, applied fast return by comparing seg
> and seg->next at the beginning of __udpv4_gso_segment_list_csum.
>
> Fixed uh->dest = *newport and iph->daddr = *newip to
> *oldport = *newport and *oldip = *newip.
>
> v4:
> Clear "Changes Requested" mark in
> https://patchwork.kernel.org/project/netdevbpf
>
> Simplified the return statement in __udp_gso_segment_list.
>
> include/net/udp.h | 2 +-
> net/ipv4/udp_offload.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++----
> net/ipv6/udp_offload.c | 2 +-
> 3 files changed, 66 insertions(+), 7 deletions(-)
>
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 877832b..01351ba 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -178,7 +178,7 @@ struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
> int udp_gro_complete(struct sk_buff *skb, int nhoff, udp_lookup_t lookup);
>
> struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> - netdev_features_t features);
> + netdev_features_t features, bool is_ipv6);
>
> static inline struct udphdr *udp_gro_udphdr(struct sk_buff *skb)
> {
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index ff39e94..cfc8726 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -187,8 +187,67 @@ struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
> }
> EXPORT_SYMBOL(skb_udp_tunnel_segment);
>
> +static void __udpv4_gso_segment_csum(struct sk_buff *seg,
> + __be32 *oldip, __be32 *newip,
> + __be16 *oldport, __be16 *newport)
> +{
> + struct udphdr *uh;
> + struct iphdr *iph;
> +
> + if (*oldip == *newip && *oldport == *newport)
> + return;
> +
> + uh = udp_hdr(seg);
> + iph = ip_hdr(seg);
> +
> + if (uh->check) {
> + inet_proto_csum_replace4(&uh->check, seg, *oldip, *newip,
> + true);
> + inet_proto_csum_replace2(&uh->check, seg, *oldport, *newport,
> + false);
> + if (!uh->check)
> + uh->check = CSUM_MANGLED_0;
> + }
> + *oldport = *newport;
> +
> + csum_replace4(&iph->check, *oldip, *newip);
> + *oldip = *newip;
> +}
> +
> +static struct sk_buff *__udpv4_gso_segment_list_csum(struct sk_buff *segs)
> +{
> + struct sk_buff *seg;
> + struct udphdr *uh, *uh2;
> + struct iphdr *iph, *iph2;
> +
> + seg = segs;
> + uh = udp_hdr(seg);
> + iph = ip_hdr(seg);
> +
> + if ((udp_hdr(seg)->dest == udp_hdr(seg->next)->dest) &&
> + (udp_hdr(seg)->source == udp_hdr(seg->next)->source) &&
> + (ip_hdr(seg)->daddr == ip_hdr(seg->next)->daddr) &&
> + (ip_hdr(seg)->saddr == ip_hdr(seg->next)->saddr))
> + return segs;
> +
> + while ((seg = seg->next)) {
> + uh2 = udp_hdr(seg);
> + iph2 = ip_hdr(seg);
> +
> + __udpv4_gso_segment_csum(seg,
> + &iph2->saddr, &iph->saddr,
> + &uh2->source, &uh->source);
> + __udpv4_gso_segment_csum(seg,
> + &iph2->daddr, &iph->daddr,
> + &uh2->dest, &uh->dest);
> + }
> +
> + return segs;
> +}
> +
> static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
> - netdev_features_t features)
> + netdev_features_t features,
> + bool is_ipv6)
> {
> unsigned int mss = skb_shinfo(skb)->gso_size;
>
> @@ -198,11 +257,11 @@ static struct sk_buff *__udp_gso_segment_list(struct sk_buff *skb,
>
> udp_hdr(skb)->len = htons(sizeof(struct udphdr) + mss);
>
> - return skb;
> + return is_ipv6 ? skb : __udpv4_gso_segment_list_csum(skb);
I don't think it's okay to fix checksums only for IPv4.
IPv6 checksum mangling doesn't depend on any code from net/ipv6. Just
use inet_proto_csum_replace16() for v6 addresses (see nf_nat_proto.c
for reference). You can guard the path for IPv6 with
IS_ENABLED(CONFIG_IPV6) to optimize IPv4-only systems a bit.
> }
>
> struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> - netdev_features_t features)
> + netdev_features_t features, bool is_ipv6)
> {
> struct sock *sk = gso_skb->sk;
> unsigned int sum_truesize = 0;
> @@ -214,7 +273,7 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
> __be16 newlen;
>
> if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
> - return __udp_gso_segment_list(gso_skb, features);
> + return __udp_gso_segment_list(gso_skb, features, is_ipv6);
>
> mss = skb_shinfo(gso_skb)->gso_size;
> if (gso_skb->len <= sizeof(*uh) + mss)
> @@ -328,7 +387,7 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
> goto out;
>
> if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
> - return __udp_gso_segment(skb, features);
> + return __udp_gso_segment(skb, features, false);
>
> mss = skb_shinfo(skb)->gso_size;
> if (unlikely(skb->len <= mss))
> diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
> index c7bd7b1..faa823c 100644
> --- a/net/ipv6/udp_offload.c
> +++ b/net/ipv6/udp_offload.c
> @@ -42,7 +42,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
> goto out;
>
> if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
> - return __udp_gso_segment(skb, features);
> + return __udp_gso_segment(skb, features, true);
>
> mss = skb_shinfo(skb)->gso_size;
> if (unlikely(skb->len <= mss))
> --
> 2.7.4
Thanks,
Al
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