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Message-ID: <201203051109.48817.hans.schillstrom@ericsson.com>
Date: Mon, 5 Mar 2012 11:09:46 +0100
From: Hans Schillstrom <hans.schillstrom@...csson.com>
To: Pablo Neira Ayuso <pablo@...filter.org>
CC: "kaber@...sh.net" <kaber@...sh.net>,
"jengelh@...ozas.de" <jengelh@...ozas.de>,
"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"hans@...illstrom.com" <hans@...illstrom.com>
Subject: Re: [v9 PATCH 2/3] NETFILTER module xt_hmark, new target for HASH based fwmark
On Sunday 04 March 2012 19:44:59 Pablo Neira Ayuso wrote:
> Hi Hans,
>
> I'm going to mix comestical request with possible issues that I find
> in this patch, please see below.
>
> On Thu, Feb 16, 2012 at 11:21:11AM +0100, Hans Schillstrom wrote:
...
> > +struct xt_hmark_info {
> > + union nf_inet_addr smask; /* Source address mask */
>
> would you mind to use more readable field names, eg. src_mask
> instead? Same thing for other fields.
Sure, no problems.
...
> > diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
> > index 40f4c3d..21bc5e8 100644
> > --- a/net/netfilter/Makefile
> > +++ b/net/netfilter/Makefile
> > @@ -57,6 +57,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_CONNSECMARK) += xt_CONNSECMARK.o
> > obj-$(CONFIG_NETFILTER_XT_TARGET_CT) += xt_CT.o
> > obj-$(CONFIG_NETFILTER_XT_TARGET_DSCP) += xt_DSCP.o
> > obj-$(CONFIG_NETFILTER_XT_TARGET_HL) += xt_HL.o
> > +obj-$(CONFIG_NETFILTER_XT_TARGET_HMARK) += xt_hmark.o
>
> Netfilter's naming policy requires that targets are in upper case.
I asked netfilter team about that, and got the answer
that it should be lower case for new modules.
Have that been changed ?
>
> > obj-$(CONFIG_NETFILTER_XT_TARGET_LED) += xt_LED.o
> > obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
> > obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o
...
> > +
> > +/*
> > + * ICMP, get header offset if icmp error
> > + */
> > +static int get_inner_hdr(struct sk_buff *skb, int iphsz, int nhoff)
> > +{
> > + const struct icmphdr *icmph;
> > + struct icmphdr _ih;
> > +
> > + /* Not enough header? */
> > + icmph = skb_header_pointer(skb, nhoff + iphsz, sizeof(_ih), &_ih);
> > + if (icmph == NULL)
> > + return nhoff;
>
> I think this has to return -1 in this case.
No, it must return the unchanged value of nhoffs.
Unless I change the usge of it as described later.
>
> > +
> > + if (icmph->type > NR_ICMP_TYPES)
> > + return nhoff;
>
> Same thing.
Same comment.
>
> > +
> > + /* Error message? */
> > + if (icmph->type != ICMP_DEST_UNREACH &&
> > + icmph->type != ICMP_SOURCE_QUENCH &&
> > + icmph->type != ICMP_TIME_EXCEEDED &&
> > + icmph->type != ICMP_PARAMETERPROB &&
> > + icmph->type != ICMP_REDIRECT)
> > + return nhoff;
> > +
> > + return nhoff + iphsz + sizeof(_ih);
> > +}
> > +
> > +#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
> > +/*
> > + * Get ipv6 header offset if icmp error
> > + */
> > +static int get_inner6_hdr(struct sk_buff *skb, int *offset)
>
> I'd suggest to return the offset like in get_inner_hdr, not need for
> one extra parameter then.
get_inner6_hdr() must return true/false not an offset
It's hard to make IPv4 & IPv6 the same due to the more complex header finding in IPv6,
Maybe IPv4 can get more like IPv6,
static int get_inner_hdr(struct sk_buff *skb, int *nhoff)
{
const struct icmphdr *icmph;
struct icmphdr _ih;
int iphz = ((struct iphdr *)skb_network_header(skb))->ihl * 4;
/* Not enough header? */
icmph = skb_header_pointer(skb, *nhoff + iphsz, sizeof(_ih), &_ih);
if (icmph == NULL || icmph->type > NR_ICMP_TYPES)
return 0;
/* Error message? */
if (icmph->type != ICMP_DEST_UNREACH &&
icmph->type != ICMP_SOURCE_QUENCH &&
icmph->type != ICMP_TIME_EXCEEDED &&
icmph->type != ICMP_PARAMETERPROB &&
icmph->type != ICMP_REDIRECT)
return 0
*nhoff += iphsz + sizeof(_ih);
return 1;
}
...
if (ip->protocol == IPPROTO_ICMP) {
/* calc hash on inner header if an icmp error */
if (get_inner_hdr(skb, &nhoff)) {
ip = skb_header_pointer(skb, nhoff, sizeof(_ip), &_ip);
if (!ip)
return XT_CONTINUE;
}
}
instead of :
if (ip->protocol == IPPROTO_ICMP) {
/* calc hash on inner header if an icmp error */
nhoff = get_inner_hdr(skb, ip->ihl * 4, nhoff);
ip = skb_header_pointer(skb, nhoff, sizeof(_ip), &_ip);
if (!ip)
return XT_CONTINUE;
}
I don't see why this should be done, maintenance ?
>
> > +{
> > + struct icmp6hdr *icmp6h, _ih6;
> > +
> > + icmp6h = skb_header_pointer(skb, *offset, sizeof(_ih6), &_ih6);
> > + if (icmp6h == NULL)
> > + return 0;
> > +
> > + if (icmp6h->icmp6_type && icmp6h->icmp6_type < 128) {
> > + *offset += sizeof(struct icmp6hdr);
> ^^
> extra space there.
>
> > + return 1;
> > + }
> > + return 0;
> > +}
> > +/*
> > + * Calculate hash based fw-mark, on the five tuple if possible.
> > + * special cases :
> > + * - Fragments do not use ports not even on the first fragment,
> > + * nf_defrag_ipv6.ko don't defrag for us like it do in ipv4.
> > + * This might be changed in the future.
> > + * - On ICMP errors the inner header will be used.
> > + * - Tunnels no ports
> > + * - ESP & AH uses SPI
> > + * @returns XT_CONTINUE
> > + */
> > +static unsigned int
> > +hmark_v6(struct sk_buff *skb, const struct xt_action_param *par)
> > +{
> > + struct xt_hmark_info *info = (struct xt_hmark_info *)par->targinfo;
> > + struct ipv6hdr *ip6, _ip6;
> > + int poff, flag = IP6T_FH_F_AUTH; /* Ports offset, find_hdr flags */
> > + u32 addr1, addr2, hash, nhoffs = 0;
> > + u8 nexthdr;
> > + union hmark_ports uports = { .v32 = 0 };
>
> I think that this can be: union hmark_ports uports = {};
I think moving the init further down is better, since there is a couple of returns before.
+ uport.v32 = 0;
+ if ((info->flags & XT_F_HMARK_METHOD_L3) ||
+ (nexthdr == IPPROTO_ICMPV6))
+ goto no6ports;
>
> > + unsigned short fragoff = 0;
> > +
> > + ip6 = (struct ipv6hdr *) (skb->data + skb_network_offset(skb));
> > +
> > + nexthdr = ipv6_find_hdr(skb, &nhoffs, -1, &fragoff, &flag);
> > + if (nexthdr < 0)
> > + return XT_CONTINUE;
> > + /* No need to check for icmp errors on fragments */
> > + if ((flag & IP6T_FH_F_FRAG) || (nexthdr != IPPROTO_ICMPV6))
> > + goto noicmp;
> > + /* if an icmp error, use the inner header */
> > + if (get_inner6_hdr(skb, &nhoffs)) {
>
> I think you have to check that nexthdr == IPPROTO_ICMPV6 here,
> otherwise non-icmp packets will be passed to get_inner6_hdr.
>
I do, (4 lines up)
+ if ((flag & IP6T_FH_F_FRAG) || (nexthdr != IPPROTO_ICMPV6))
+ goto noicmp;
> > + ip6 = skb_header_pointer(skb, nhoffs, sizeof(_ip6), &_ip6);
> > + if (!ip6)
> > + return XT_CONTINUE;
> > + /* Treat AH as ESP */
>
> This comments means: try to find auth headers if possible, right?
No, It might be a litle bit unclean but earlier Patric, you and I brought it up,
- the descending into AH and port searching.
I think the comment should be some thing like,
/* Treat AH as ESP, use SPI nothing else. */
>
> > + flag = IP6T_FH_F_AUTH;
> > + nexthdr = ipv6_find_hdr(skb, &nhoffs, -1, &fragoff, &flag);
> > + if (nexthdr < 0)
> > + return XT_CONTINUE;
> > + }
> > +noicmp:
> > + addr1 = (__force u32)
> > + (ip6->saddr.s6_addr32[0] & info->smask.in6.s6_addr32[0]) ^
> > + (ip6->saddr.s6_addr32[1] & info->smask.in6.s6_addr32[1]) ^
> > + (ip6->saddr.s6_addr32[2] & info->smask.in6.s6_addr32[2]) ^
> > + (ip6->saddr.s6_addr32[3] & info->smask.in6.s6_addr32[3]);
> > + addr2 = (__force u32)
> > + (ip6->daddr.s6_addr32[0] & info->dmask.in6.s6_addr32[0]) ^
> > + (ip6->daddr.s6_addr32[1] & info->dmask.in6.s6_addr32[1]) ^
> > + (ip6->daddr.s6_addr32[2] & info->dmask.in6.s6_addr32[2]) ^
> > + (ip6->daddr.s6_addr32[3] & info->dmask.in6.s6_addr32[3]);
> > +
> > + if ((info->flags & XT_F_HMARK_METHOD_L3) ||
> > + (nexthdr == IPPROTO_ICMPV6))
> > + goto no6ports;
> > + /* Is next header valid for port or SPI calculation ? */
> > + poff = proto_ports_offset(nexthdr);
> > + if ((flag & IP6T_FH_F_FRAG) || poff < 0)
> > + return XT_CONTINUE;
> > +
> > + nhoffs += poff;
> > + /* Since uports is modified, skb_header_pointer() can't be used */
>
> Why not? You can pass &uports to skb_header_pointer, it takes a
> generic pointer.
uports is a local var that will written into later (swap and mask),
The comment is there becuse of that.
>
> > + if (!pskb_may_pull(skb, nhoffs + 4))
> > + return XT_CONTINUE;
> > + uports.v32 = * (__force u32 *) (skb->data + nhoffs);
> > +
> > + if ((nexthdr == IPPROTO_ESP) || (nexthdr == IPPROTO_AH))
> > + uports.v32 = (uports.v32 & info->spimask) | info->spiset;
> > + else {
> > + uports.v32 = (uports.v32 & info->pmask.v32) | info->pset.v32;
> > + /* get a consistent hash (same value on both flow directions) */
> > + if (uports.p16.dst < uports.p16.src)
> > + swap(uports.p16.dst, uports.p16.src);
> > + }
> > +
> > +no6ports:
> > + nexthdr &= info->prmask;
> > + /* get a consistent hash (same value on both flow directions) */
> > + if (addr2 < addr1)
> > + swap(addr1, addr2);
> > +
> > + hash = jhash_3words(addr1, addr2, uports.v32, info->hashrnd) ^ nexthdr;
> > + skb->mark = (hash % info->hmod) + info->hoffs;
> > + return XT_CONTINUE;
> > +}
> > +#endif
> > +/*
> > + * Calculate hash based fw-mark, on the five tuple if possible.
> > + * special cases :
> > + * - Fragments do not use ports not even on the first fragment,
> > + * unless nf_defrag_xx.ko is used.
> > + * - On ICMP errors the inner header will be used.
> > + * - Tunnels no ports
> > + * - ESP & AH uses SPI
> > + * @returns XT_CONTINUE
> > + */
> > +static unsigned int
> > +hmark_v4(struct sk_buff *skb, const struct xt_action_param *par)
> > +{
> > + struct xt_hmark_info *info = (struct xt_hmark_info *)par->targinfo;
> > + int nhoff, poff, frag = 0;
> > + struct iphdr *ip, _ip;
> > + u8 ip_proto;
> > + u32 addr1, addr2, hash;
> > + u16 snatport = 0, dnatport = 0;
> > + union hmark_ports uports;
> > + enum ip_conntrack_info ctinfo;
> > + struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
>
> You spend cycles initializing this variable, but you may not use it.
Yes, it can be improved ...
> For the conntrack case, you can make in the very beginning:
>
> if (info->flags & XT_HMARK_CT) {
> struct nf_conn *ct = nf_ct_get(skb, &ctinfo);
>
> if (ct && !nf_ct_is_untracked(ct)) {
> struct nf_conntrack_tuple *otuple =
> &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
> struct nf_conntrack_tuple *rtuple =
> &ct->tuplehash[IP_CT_DIR_REPLY].tuple;
>
> addr_src = (__force u32) otuple->src.u3.in.s_addr;
> port_src = otuple->src.u.all;
> addr_dst = (__force u32) rtuple->src.u3.in.s_addr;
> port_dst = rtuple->src.u.all;
> } else
> return XT_CONTINUE;
> }
>
> With SNAT/masquerade:
> original: A -> B
> reply: B -> FW
>
> With DNAT:
> original: A -> FW
> reply: B -> A
>
> So real addresses are always source for the original tuple and source
> for the reply tuple.
>
> I think it's better just to tell HMARK to use CT, no need to specify
> what part of it, it's simple and the user will not get confused
> selecting wrong configurations.
>
We discussed that and you wrote:
"My opinion is that the user must have total control on the target
behaviour through the configuration options."
...
"I'm fine if you allow to select what tuple you want to use to hash."
Have you changed you opinion ?
>From my point of view it doesn't matter.
> Note that if you didn't not select to use conntrack, we default on the
> packet-based version for HMARK which makes all the fragmentation
> handling and so on.
>
> Again, I'm proposing you to use addr_src and addr_dst instead of addr1
> and addr2 for readability.
>
> And remove the extra white extra line here below.
>
> > +
> > +
> > + nhoff = skb_network_offset(skb);
> > + uports.v32 = 0;
>
> Better initialize this in the variable definition.
or beter, move it to just before:
+ uports.v32 = 0;
+ if ((info->flags & XT_F_HMARK_METHOD_L3) || (ip_proto == IPPROTO_ICMP))
+ goto noports;
>
> > +
> > + ip = (struct iphdr *) (skb->data + nhoff);
> > + if (ip->protocol == IPPROTO_ICMP) {
> > + /* calc hash on inner header if an icmp error */
> > + nhoff = get_inner_hdr(skb, ip->ihl * 4, nhoff);
>
> This may return
>
> > + ip = skb_header_pointer(skb, nhoff, sizeof(_ip), &_ip);
> > + if (!ip)
> > + return XT_CONTINUE;
> > + }
> > +
> > + ip_proto = ip->protocol;
> > + if (ip->frag_off & htons(IP_MF | IP_OFFSET))
> > + frag = 1;
> > +
> > + addr1 = (__force u32) ip->saddr;
> > + addr2 = (__force u32) ip->daddr;
> > +
> > +#if IS_ENABLED(CONFIG_NF_CONNTRACK)
> > + if (ct && !nf_ct_is_untracked(ct)) {
> > + struct nf_conntrack_tuple *otuple =
> > + &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
> > +
> > + if (info->flags & XT_HMARK_CT_OSRC) {
> > + addr1 = (__force u32) otuple->dst.u3.in.s_addr;
> > + dnatport = otuple->dst.u.udp.port;
> > + }
> > + if ((ct->status & IPS_SRC_NAT) &&
> ^^^^^^^^^^
> This seems to have slipped through BTW.
Oops
>
> > + (info->flags & XT_HMARK_CT_ODST)) {
> > + addr2 = (__force u32) otuple->src.u3.in.s_addr;
> > + snatport = otuple->src.u.udp.port;
> > + }
> > + }
> > +#endif
> > + addr1 &= info->smask.ip;
> > + addr2 &= info->dmask.ip;
> > +
> > + if ((info->flags & XT_F_HMARK_METHOD_L3) || (ip_proto == IPPROTO_ICMP))
> > + goto noports;
> > + /* Check if ports can be used in hash calculation. */
> > + poff = proto_ports_offset(ip_proto);
> > + if (frag || poff < 0)
> > + return XT_CONTINUE;
> > +
> > + nhoff += (ip->ihl * 4) + poff;
> > + if (!pskb_may_pull(skb, nhoff + 4))
> > + return XT_CONTINUE;
> > +
> > + uports.v32 = * (__force u32 *) (skb->data + nhoff);
> > + if (ip_proto == IPPROTO_ESP || ip_proto == IPPROTO_AH)
> > + uports.v32 = (uports.v32 & info->spimask) | info->spiset;
> > + else {
> > + if (snatport) /* Replace nat'ed port(s) */
> > + uports.p16.dst = snatport;
> > + if (dnatport)
> > + uports.p16.src = dnatport;
> > + uports.v32 = (uports.v32 & info->pmask.v32) |
> > + info->pset.v32;
> > + /* get a consistent hash (same value on both flow directions) */
> > + if (uports.p16.dst < uports.p16.src)
> > + swap(uports.p16.src, uports.p16.dst);
> > + }
> > +
> > +noports:
> > + ip_proto &= info->prmask;
> > + /* get a consistent hash (same value on both flow directions) */
> > + if (addr2 < addr1)
> > + swap(addr1, addr2);
> > +
> > + hash = jhash_3words(addr1, addr2, uports.v32, info->hashrnd) ^ ip_proto;
> > + skb->mark = (hash % info->hmod) + info->hoffs;
> > + return XT_CONTINUE;
> > +}
> > +
> > +static int hmark_check(const struct xt_tgchk_param *par)
> > +{
> > + const struct xt_hmark_info *info = par->targinfo;
> > +
> > + if (!info->hmod) {
> > + pr_info("HMARK: hmark-mod can't be zero\n");
> > + return -EINVAL;
> > + }
> > + if (info->prmask && (info->flags & XT_F_HMARK_METHOD_L3)) {
> > + pr_info("HMARK: When method L3 proto mask must be zero\n");
> > + return -EINVAL;
> > + }
> > + return 0;
> > +}
> > +
> > +static struct xt_target hmark_tg_reg[] __read_mostly = {
> > + {
> > + .name = "HMARK",
> > + .revision = 0,
> > + .family = NFPROTO_IPV4,
> > + .target = hmark_v4,
> > + .targetsize = sizeof(struct xt_hmark_info),
> > + .checkentry = hmark_check,
> > + .me = THIS_MODULE,
> > + },
> > +#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
> > + {
> > + .name = "HMARK",
> > + .revision = 0,
> > + .family = NFPROTO_IPV6,
> > + .target = hmark_v6,
> > + .targetsize = sizeof(struct xt_hmark_info),
> > + .checkentry = hmark_check,
> > + .me = THIS_MODULE,
> > + },
> > +#endif
> > +};
> > +
> > +static int __init hmark_mt_init(void)
> > +{
> > + int ret;
> > +
> > + ret = xt_register_targets(hmark_tg_reg, ARRAY_SIZE(hmark_tg_reg));
> > + if (ret < 0)
> > + return ret;
> > + return 0;
> > +}
> > +
> > +static void __exit hmark_mt_exit(void)
> > +{
> > + xt_unregister_targets(hmark_tg_reg, ARRAY_SIZE(hmark_tg_reg));
> > +}
> > +
> > +module_init(hmark_mt_init);
> > +module_exit(hmark_mt_exit);
> > --
> > 1.7.2.3
> >
>
--
Thanks
Hans Schillstrom
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