Re: tcp hostcache and ip fastforward for review

From: Jesper Skriver <jesper_at_FreeBSD.org>
Date: Wed, 12 Nov 2003 23:53:26 +0100
On Sun, Nov 09, 2003 at 05:19:07PM +0100, Andre Oppermann wrote:
> Hello all,
> 
> this patch contains three things (to be separated for committing):
> 
>  tcp_hostcache
> 
>   - removes protocol cloning from routing table (IPv4+6)
>   - removes rtentry pointer from inpcb and in6pcb
>   - removes ip route cache in ip_input.c (locking much easier)
>   - removes most (tcp specific) metrics from rtentry metrics
>   - adds a hostcache table which carries the metrics for tcp
>   - works transparently for IPv4 and IPv6
>   - is designed for concurrent access in SMP environments
>   - significant reduction of routing table size (no cloning anymore)
>   - eases many routing table locking situations in ip/tcp code
> 
>  ip_fastforward
> 
>   - removes ip_flow forwarding code
>   - adds full direct process-to-completion IPv4 forwarding code
>   - handles ip fragmentation incl. hw support (ip_flow did not)
>   - supports ipfw and ipfilter (ip_flow did not)
>   - supports divert and ipfw fwd (ip_flow did not)
>   - drops anything it can't handle back to normal ip_input

I have a few comments to this code, see inline, look for #jesper

Apart from that it looks good.

/Jesper

> +int
> +ip_fastforward(struct mbuf *m)
> +{
> +	struct ip *ip;
> +	struct mbuf *m0 = NULL;
> +#ifdef IPDIVERT
> +	struct ip *tip;
> +	struct mbuf *teem = NULL;
> +#endif
> +	struct mbuf *tag = NULL;
> +	struct route ro;
> +	struct sockaddr_in *dst = NULL;
> +	struct in_ifaddr *ia = NULL;
> +	struct ifaddr *ifa = NULL;
> +	struct ifnet *ifp = NULL;
> +	struct ip_fw_args args;
> +	in_addr_t odest, dest;
> +	u_short sum;
> +	int hlen;
> +	int error = 0;
> +	int ipfw;
> +
> +	/*
> +	 * Are we active and forwarding packets?
> +	 */
> +	if (!ipfastforward_active || !ipforwarding)
> +		return 0;
> +
> +	/*
> +	 * If there is any MT_TAG we fall back to ip_input because we can't
> +	 * handle TAGs here.
> +	 */
> +	if (m && m->m_type == MT_TAG)
> +		return 0;
> +
> +	M_ASSERTVALID(m);
> +	M_ASSERTPKTHDR(m);
> +

[...]

> +
> +	/*
> +	 * Only unicast IP, not from loopback, no L2 or IP broadcast,
> +	 * no multicast, no INADDR_ANY
> +	 */
> +	if ((m->m_pkthdr.rcvif->if_flags & IFF_LOOPBACK) ||
> +	    (ntohl(ip->ip_src.s_addr) == (u_long)INADDR_BROADCAST) ||

#jesper
You will never see packets with a multicast source address.

> +	    (ntohl(ip->ip_dst.s_addr) == (u_long)INADDR_BROADCAST) ||
> +	    (IN_MULTICAST(ntohl(ip->ip_src.s_addr))) ||
> +	    (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) ||
> +	    (ip->ip_dst.s_addr == INADDR_ANY) )
> +		goto fallback;
> +
> +	/*
> +	 * Is it for a local address on this host?
> +	 */
> +	LIST_FOREACH(ia, INADDR_HASH(ip->ip_dst.s_addr), ia_hash) {
> +		if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_dst.s_addr) {
> +			goto fallback;
> +		}
> +	}
> +
> +	/*
> +	 * Or is it for a local IP broadcast address on this host?
> +	 */
> +	if (m->m_pkthdr.rcvif->if_flags & IFF_BROADCAST) {
> +	        TAILQ_FOREACH(ifa, &m->m_pkthdr.rcvif->if_addrhead, ifa_link) {
> +			if (ifa->ifa_addr->sa_family != AF_INET)
> +				continue;
> +			ia = ifatoia(ifa);
> +			if (ia->ia_netbroadcast.s_addr == ip->ip_dst.s_addr)
> +				goto fallback;
> +			if (satosin(&ia->ia_broadaddr)->sin_addr.s_addr ==
> +			    ip->ip_dst.s_addr)
> +				goto fallback;
> +			continue;
> +fallback:
> +			/* drop the packet back to netisr */
> +			ip->ip_len = htons(ip->ip_len);
> +			ip->ip_off = htons(ip->ip_off);
> +			return 0;
> +		}
> +	}
> +	ipstat.ips_total++;

#jesper
If we stored special "for us" /32 routes in the routing table for
addresses configured on this host, we could avoid the above 2 loops,
which can quite expensive.

These special routes will simply mean that the packet is for us, and
needs to given to ip_input

> +	/**
> +	 ** Third: incoming packet firewall processing
> +	 **/
> +
> +	odest = dest = ip->ip_dst.s_addr;

#jesper
You could save a few cycles by doing

#ifdef PFIL_HOOKS
	odest = ip->ip_dst.s_addr;
	/*
	 * Run through list of ipfilter hooks for input packets
	 */
	if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN) ||
	    m == NULL)
		return 1;

	M_ASSERTVALID(m);
	M_ASSERTPKTHDR(m);

	ip = mtod(m, struct ip *);	/* if m changed during fw processing */
	dest = ip->ip_dst.s_addr;
#else
	odest = dest = ip->ip_dst.s_addr;
#endif

Thus avoiding writing to dest twice.

> +#ifdef PFIL_HOOKS
> +	/*
> +	 * Run through list of ipfilter hooks for input packets
> +	 */
> +	if (pfil_run_hooks(&inet_pfil_hook, &m, m->m_pkthdr.rcvif, PFIL_IN) ||
> +	    m == NULL)
> +		return 1;
> +
> +	M_ASSERTVALID(m);
> +	M_ASSERTPKTHDR(m);
> +
> +	ip = mtod(m, struct ip *);	/* if m changed during fw processing */
> +	dest = ip->ip_dst.s_addr;
> +#endif
> +
> +	/*
> +	 * Run through ipfw for input packets
> +	 */
> +	if (fw_enable && IPFW_LOADED) {
> +		bzero(&args, sizeof(args));
> +		args.m = m;
> +		ipfw = 0;
> +
> +		ipfw = ip_fw_chk_ptr(&args);
> +		m = args.m;
> +
> +		M_ASSERTVALID(m);
> +		M_ASSERTPKTHDR(m);
> +
> +		/*
> +		 * Packet denied, drop it
> +		 */
> +		if ( (ipfw & IP_FW_PORT_DENY_FLAG) || m == NULL) {
> +			if (m)
> +				m_freem(m);
> +			return 1;
> +		}
> +		/*
> +		 * Send packet to the appropriate pipe
> +		 */
> +                if (DUMMYNET_LOADED && (ipfw & IP_FW_PORT_DYNT_FLAG) != 0) {

#jesper 

Whitespace bug, spaces instead of tabs

> +			ip_dn_io_ptr(m, ipfw & 0xffff, DN_TO_IP_IN, &args);
> +			return 1;
> +		}
> +#ifdef IPDIVERT
> +		/*
> +		 * Divert packet
> +		 */
> +		if (ipfw != 0 && (ipfw & IP_FW_PORT_DYNT_FLAG) == 0) {
> +			/*
> +			 * See if this is a fragment
> +			 */
> +			if (ip->ip_off & (IP_MF | IP_OFFMASK)) {
> +				MGETHDR(tag, M_DONTWAIT, MT_TAG);
> +				if (tag == NULL) {
> +					m_freem(m);
> +					return 1;
> +				}
> +				tag->m_flags = PACKET_TAG_DIVERT;
> +				tag->m_data = (caddr_t)(u_long)args.divert_rule;
> +				tag->m_next = m;
> +				m = tag;
> +				tag = NULL;
> +
> +                                goto droptoours;

#jesper 

Whitespace bug, spaces instead of tabs

> +			}
> +			/*
> +			 * Tee packet
> +			 */
> +			if ((ipfw & IP_FW_PORT_TEE_FLAG) != 0)
> +				teem = m_dup(m, M_DONTWAIT);
> +			else
> +				teem = m;
> +			if (teem == NULL)
> +				goto passin;
> +
> +			M_ASSERTVALID(teem);
> +			M_ASSERTPKTHDR(teem);
> +
> +			/*
> +			 * Delayed checksums are not compatible
> +			 */
> +			if (teem->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
> +				in_delayed_cksum(teem);
> +				teem->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
> +			}
> +			/*
> +			 * Restore packet header fields to original values
> +			 */
> +			tip = mtod(teem, struct ip *);
> +			tip->ip_len = htons(tip->ip_len);
> +			tip->ip_off = htons(tip->ip_off);
> +			/*
> +			 * Deliver packet to divert input routine
> +			 */
> +			divert_packet(teem, 0, ipfw & 0xffff, args.divert_rule);
> +			/*
> +			 * If this was not tee, we are done
> +			 */
> +			if ((ipfw & IP_FW_PORT_TEE_FLAG) == 0)
> +				return 1;
> +			/* Continue if it was tee */
> +			goto passin;
> +		}
> +#endif
> +		if (ipfw == 0 && args.next_hop != NULL) {
> +			dest = args.next_hop->sin_addr.s_addr;
> +			goto passin;
> +		}
> +		/*
> +		 * Let through or not?
> +		 */
> +		if (ipfw != 0) {
> +			m_freem(m);
> +			return 1;
> +		}
> +	}
> +passin:
> +	ip = mtod(m, struct ip *);	/* if m changed during fw processing */
> +
> +	/*
> +	 * Destination address changed?
> +	 */
> +	if (odest != dest) {
> +		/*
> +		 * Is it now for a local address on this host?
> +		 */
> +		LIST_FOREACH(ia, INADDR_HASH(ip->ip_dst.s_addr), ia_hash) {
> +			if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_dst.s_addr)
> +				goto forwardlocal;
> +		}

#jesper

Same comment as above - and do we really want to see if the original
destination address was ours if we're doing NAT ?

> +		/*
> +		 * Go on with new destination address
> +		 */
> +	}
> +
> +	M_ASSERTVALID(m);
> +	M_ASSERTPKTHDR(m);
> +
> +	/**
> +	 ** Forth: decrement TTL and look up route
> +	 **/
> +
> +	/*
> +	 * Check TTL
> +	 */
> +#ifdef IPSTEALTH
> +	if (!ipstealth) {
> +#endif
> +	if (ip->ip_ttl <= IPTTLDEC) {
> +		icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, NULL, NULL);
> +		return 1;
> +	}
> +
> +	/*
> +	 * Decrement the TTL and incrementally change the checksum.
> +	 * Don't bother doing this with hw checksum offloading.
> +	 */
> +	ip->ip_ttl -= IPTTLDEC;
> +	if (ip->ip_sum >= (u_int16_t) ~htons(IPTTLDEC << 8))
> +		ip->ip_sum -= ~htons(IPTTLDEC << 8);
> +	else
> +		ip->ip_sum += htons(IPTTLDEC << 8);
> +#ifdef IPSTEALTH
> +	}
> +#endif
> +
> +	/*
> +	 * Find route to destination.
> +	 */
> +	bzero(&ro, sizeof(ro));
> +	dst = (struct sockaddr_in *)&ro.ro_dst;
> +	dst->sin_family = AF_INET;
> +	dst->sin_len = sizeof(*dst);
> +	dst->sin_addr.s_addr = dest;
> +	rtalloc(&ro);
> +
> +	/*
> +	 * Route there and interface still up?
> +	 */
> +	if ((ro.ro_rt) &&
> +	    (ro.ro_rt->rt_flags & RTF_UP) &&
> +	    (ro.ro_rt->rt_ifp->if_flags & IFF_UP)) {
> +		ia = ifatoia(ro.ro_rt->rt_ifa);
> +		ifp = ro.ro_rt->rt_ifp;
> +		if (ro.ro_rt->rt_flags & RTF_GATEWAY)
> +			dst = (struct sockaddr_in *)ro.ro_rt->rt_gateway;
> +	} else {
> +		ipstat.ips_noroute++;
> +		ipstat.ips_cantforward++;
> +		icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, NULL, NULL);
> +		if (ro.ro_rt)
> +			RTFREE(ro.ro_rt);
> +		return 1;
> +	}
> +
> +
> +	/**
> +	 ** Fifth: outgoing firewall packet processing
> +	 **/
> +
> +#ifdef PFIL_HOOKS
> +	/*
> +	 * Run through list of hooks for output packets.
> +	 */
> +	if (pfil_run_hooks(&inet_pfil_hook, &m, ifp, PFIL_OUT) ||
> +	    m == NULL) {
> +		RTFREE(ro.ro_rt);
> +		return 1;
> +	}
> +
> +	M_ASSERTVALID(m);
> +	M_ASSERTPKTHDR(m);
> +
> +	ip = mtod(m, struct ip *);
> +	dest = ip->ip_dst.s_addr;
> +#endif
> +	if (fw_enable && IPFW_LOADED && !args.next_hop) {
> +                bzero(&args, sizeof(args));
> +		args.m = m;
> +		args.oif = ifp;
> +                ipfw = 0;
> +
> +		ipfw = ip_fw_chk_ptr(&args);
> +		m = args.m;
> +
> +		M_ASSERTVALID(m);
> +		M_ASSERTPKTHDR(m);
> +
> +		if ( (ipfw & IP_FW_PORT_DENY_FLAG) || m == NULL) {
> +			if (m)
> +				m_freem(m);
> +			RTFREE(ro.ro_rt);
> +			return 1;
> +		}
> +                if (DUMMYNET_LOADED && (ipfw & IP_FW_PORT_DYNT_FLAG) != 0) {

#jesper 

Whitespace bug, spaces instead of tabs

> +			/*
> +			 * XXX note: if the ifp or rt entry are deleted
> +			 * while a pkt is in dummynet, we are in trouble!
> +			 */
> +			args.ro = &ro;		/* dummynet does not save it */
> +			args.dst = dst;
> +
> +			ip_dn_io_ptr(m, ipfw & 0xffff, DN_TO_IP_OUT, &args);
> +			RTFREE(ro.ro_rt);
> +			return 1;
> +		}
> +#ifdef IPDIVERT
> +		if (ipfw != 0 && (ipfw & IP_FW_PORT_DYNT_FLAG) == 0) {
> +			/*
> +			 * See if this is a fragment
> +			 */
> +			if (ip->ip_off & (IP_MF | IP_OFFMASK)) {
> +				MGETHDR(tag, M_DONTWAIT, MT_TAG);
> +				if (tag == NULL) {
> +					m_freem(m);
> +					RTFREE(ro.ro_rt);
> +					return 1;
> +				}
> +				tag->m_flags = PACKET_TAG_DIVERT;
> +				tag->m_data = (caddr_t)(u_int32_t)args.divert_rule;
> +				tag->m_next = m;
> +				m = tag;
> +				tag = NULL;
> +
> +				goto droptoours;
> +			}
> +			/*
> +			 * Tee packet
> +			 */
> +			if ((ipfw & IP_FW_PORT_TEE_FLAG) != 0)
> +				teem = m_dup(m, M_DONTWAIT);
> +			else
> +				teem = m;
> +			if (teem == NULL)
> +				goto passout;
> +
> +			M_ASSERTVALID(m);
> +			M_ASSERTPKTHDR(m);
> +
> +			/*
> +			 * delayed checksums are not compatible with divert
> +			 */
> +			if (teem->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
> +				in_delayed_cksum(teem);
> +				teem->m_pkthdr.csum_flags &= ~CSUM_DELAY_DATA;
> +			}
> +			/*
> +			 * Restore packet header fields to original values
> +			 */
> +			tip = mtod(teem, struct ip *);
> +			tip->ip_len = htons(tip->ip_len);
> +			tip->ip_off = htons(tip->ip_off);
> +			/*
> +			 * Deliver packet to divert input routine
> +			 */
> +			divert_packet(teem, 0, ipfw & 0xffff, args.divert_rule);
> +			/*
> +			 * If this was not tee, we are done
> +			 */
> +			if ((ipfw & IP_FW_PORT_TEE_FLAG) == 0) {
> +				RTFREE(ro.ro_rt);
> +				return 1;
> +			}
> +			/* Continue if it was tee */
> +			goto passout;
> +		}
> +#endif
> +		if (ipfw == 0 && args.next_hop != NULL) {
> +			dest = args.next_hop->sin_addr.s_addr;
> +			goto passout;
> +		}
> +		/*
> +		 * Let through or not?
> +		 */
> +		if (ipfw != 0) {
> +			m_freem(m);
> +			return 1;
> +		}
> +	}
> +passout:
> +	ip = mtod(m, struct ip *);
> +
> +	/*
> +	 * Destination address changed?
> +	 */
> +	if (odest != dest) {
> +		/*
> +		 * Is it now for a local address on this host?
> +		 */

#jesper

Again, do we really want to look for packets destined for us after being
translated ?

> +		LIST_FOREACH(ia, INADDR_HASH(ip->ip_dst.s_addr), ia_hash) {
> +			if (IA_SIN(ia)->sin_addr.s_addr == ip->ip_dst.s_addr) {
> +forwardlocal:
> +				if(args.next_hop) {
> +					MGETHDR(tag, M_DONTWAIT, MT_TAG);
> +					if (tag == NULL) {
> +						m_freem(m);
> +						if(ro.ro_rt)
> +							RTFREE(ro.ro_rt);
> +						return 1;
> +					}
> +					tag->m_flags = PACKET_TAG_IPFORWARD;
> +					tag->m_data = (caddr_t)args.next_hop;
> +					tag->m_next = m;
> +					m = tag;
> +					tag = NULL;
> +				}
> +#ifdef IPDIVERT
> +droptoours:	/* Used for DIVERT */
> +#endif
> +				MGETHDR(tag, M_DONTWAIT, MT_TAG);
> +				if (tag == NULL) {
> +					m_freem(m);
> +					if(ro.ro_rt)
> +						RTFREE(ro.ro_rt);
> +					return 1;
> +				}
> +                                tag->m_flags = PACKET_TAG_IPFASTFWD_OURS;
> +                                tag->m_data = NULL;
> +                                tag->m_next = m;

#jesper 

Whitespace bug, spaces instead of tabs

> +				m = tag;
> +				tag = NULL;
> +
> +#if 0
> +				/*
> +				 * Do some checks, we never know what fw has
> +				 * done to it.
> +				 */
> +				if (m->m_pkthdr.rcvif == NULL)
> +					m->m_pkthdr.rcvif = ifunit("lo0");
> +				if (m->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
> +					m->m_pkthdr.csum_flags |=
> +					    CSUM_DATA_VALID | CSUM_PSEUDO_HDR;
> +					m->m_pkthdr.csum_data = 0xffff;
> +				}
> +				m->m_pkthdr.csum_flags |=
> +				    CSUM_IP_CHECKED | CSUM_IP_VALID;
> +#endif
> +
> +				/* ip still points to the real packet */
> +				ip->ip_len = htons(ip->ip_len);
> +				ip->ip_off = htons(ip->ip_off);
> +
> +				M_ASSERTVALID(m);
> +
> +				/*
> +				 * Drop packet to ip_input
> +				 */
> +				if (ro.ro_rt)
> +					RTFREE(ro.ro_rt);
> +				return 0;
> +			}
> +		}
> +		/*
> +		 * Redo route lookup with new destination address
> +		 */
> +		RTFREE(ro.ro_rt);
> +		bzero(&ro, sizeof(ro));
> +		dst = (struct sockaddr_in *)&ro.ro_dst;
> +		dst->sin_family = AF_INET;
> +		dst->sin_len = sizeof(*dst);
> +		dst->sin_addr.s_addr = dest;
> +		rtalloc(&ro);
> +
> +		/*
> +		 * Route there and interface still up?
> +		 */
> +		if ((ro.ro_rt) &&
> +		    (ro.ro_rt->rt_flags & RTF_UP) &&
> +		    (ro.ro_rt->rt_ifp->if_flags & IFF_UP)) {
> +			ia = ifatoia(ro.ro_rt->rt_ifa);
> +			ifp = ro.ro_rt->rt_ifp;
> +			if (ro.ro_rt->rt_flags & RTF_GATEWAY)
> +				dst = (struct sockaddr_in *)ro.ro_rt->rt_gateway;
> +		} else {
> +			ipstat.ips_noroute++;
> +			ipstat.ips_cantforward++;
> +			icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, NULL, NULL);
> +			if (ro.ro_rt)
> +				RTFREE(ro.ro_rt);
> +			return 1;
> +		}
> +	}
> +
> +	M_ASSERTVALID(m);
> +	M_ASSERTPKTHDR(m);
> +
> +	/**
> +	 ** Sixth: send off the packet
> +	 **/
> +
> +	/*
> +	 * Check if packet fits MTU or if hardware will fragement for us
> +	 */
> +	if (ip->ip_len <= ifp->if_mtu || (ifp->if_hwassist & CSUM_FRAGMENT &&
> +	   ((ip->ip_off & IP_DF) == 0))) {
> +		/*
> +		 * Restore packet header fields to original values
> +		 */
> +		ip->ip_len = htons(ip->ip_len);
> +		ip->ip_off = htons(ip->ip_off);
> +		/*
> +		 * Send off the packet via outgoing interface
> +		 */
> +		error = (ifp->if_output)(ifp, m, (struct sockaddr *)dst, ro.ro_rt);
> +		if (ia) {
> +			ia->ia_ifa.if_opackets++;
> +			ia->ia_ifa.if_obytes += m->m_pkthdr.len;
> +		}
> +	} else {
> +		/*
> +		 * Handle EMSGSIZE with icmp reply needfrag for TCP MTU discovery
> +		 */
> +		if (ip->ip_off & IP_DF) {
> +			icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_NEEDFRAG, NULL, ifp);
> +			ipstat.ips_cantfrag++;
> +			RTFREE(ro.ro_rt);
> +			return 1;
> +		} else {
> +			/*
> +			 * We have to fragement the packet
> +			 */
> +			m->m_pkthdr.csum_flags |= CSUM_IP;
> +			if (ip_fragment(ip, &m, ifp->if_mtu, ifp->if_hwassist,
> +					(~ifp->if_hwassist & CSUM_DELAY_IP))) {
> +				m_freem(m);
> +				RTFREE(ro.ro_rt);
> +				return 1;
> +			}
> +			/*
> +			 * Send off the fragments via outgoing interface
> +			 */
> +			for (; m; m = m0) {
> +				m0 = m->m_nextpkt;
> +				m->m_nextpkt = 0;
> +
> +				M_ASSERTVALID(m);
> +				M_ASSERTPKTHDR(m);
> +
> +				if (error == 0) {
> +					error = (*ifp->if_output)(ifp, m,
> +						(struct sockaddr *)dst, ro.ro_rt);
> +					if (ia) {
> +						ia->ia_ifa.if_opackets++;
> +						ia->ia_ifa.if_obytes += m->m_pkthdr.len;
> +					}
> +				} else {
> +					m_freem(m);
> +				}
> +			}
> +			if (error == 0)
> +				ipstat.ips_fragmented++;
> +		}
> +	}
> +
> +	if (error == ENOBUFS)
> +		ipstat.ips_odropped++;
> +	else if (error != 0)
> +		ipstat.ips_odropped++;
> +	else {
> +		ro.ro_rt->rt_rmx.rmx_pksent++;
> +		ipstat.ips_forward++;
> +		ipstat.ips_fastforward++;
> +	}
> +	RTFREE(ro.ro_rt);
> +	return 1;
> +}
> +
Received on Wed Nov 12 2003 - 13:53:30 UTC

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