Skip to content

Commit

Permalink
datapath: Remove tunnel path MTU discovery support.
Browse files Browse the repository at this point in the history 
Path MTU discovery can improve tunnel performance in some cases
but is non-standard and can introduce problems in others.  As a
result it has already been deprecated and removed from userspace.
This removes the corresponding kernel support to simplify the
code.

Signed-off-by: Jesse Gross <[email protected]>
Acked-by: Kyle Mestery <[email protected]>
  • Loading branch information
@jessegross
jessegross committed Jan 28, 2013
1 parent 8a9ff93 commit 78adaee
Show file tree
Hide file tree
Showing 4 changed files with 6 additions and 471 deletions.
348 changes: 4 additions & 344 deletions datapath/tunnel.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -358,343 +358,6 @@ void ovs_tnl_rcv(struct vport *vport, struct sk_buff *skb)
ovs_vport_receive(vport, skb);
}

static bool check_ipv4_address(__be32 addr)
{
if (ipv4_is_multicast(addr) || ipv4_is_lbcast(addr)
|| ipv4_is_loopback(addr) || ipv4_is_zeronet(addr))
return false;

return true;
}

static bool ipv4_should_icmp(struct sk_buff *skb)
{
struct iphdr *old_iph = ip_hdr(skb);

/* Don't respond to L2 broadcast. */
if (is_multicast_ether_addr(eth_hdr(skb)->h_dest))
return false;

/* Don't respond to L3 broadcast or invalid addresses. */
if (!check_ipv4_address(old_iph->daddr) ||
!check_ipv4_address(old_iph->saddr))
return false;

/* Only respond to the first fragment. */
if (old_iph->frag_off & htons(IP_OFFSET))
return false;

/* Don't respond to ICMP error messages. */
if (old_iph->protocol == IPPROTO_ICMP) {
u8 icmp_type, *icmp_typep;

icmp_typep = skb_header_pointer(skb, (u8 *)old_iph +
(old_iph->ihl << 2) +
offsetof(struct icmphdr, type) -
skb->data, sizeof(icmp_type),
&icmp_type);

if (!icmp_typep)
return false;

if (*icmp_typep > NR_ICMP_TYPES
|| (*icmp_typep <= ICMP_PARAMETERPROB
&& *icmp_typep != ICMP_ECHOREPLY
&& *icmp_typep != ICMP_ECHO))
return false;
}

return true;
}

static void ipv4_build_icmp(struct sk_buff *skb, struct sk_buff *nskb,
unsigned int mtu, unsigned int payload_length)
{
struct iphdr *iph, *old_iph = ip_hdr(skb);
struct icmphdr *icmph;
u8 *payload;

iph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
icmph = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
payload = skb_put(nskb, payload_length);

/* IP */
iph->version = 4;
iph->ihl = sizeof(struct iphdr) >> 2;
iph->tos = (old_iph->tos & IPTOS_TOS_MASK) |
IPTOS_PREC_INTERNETCONTROL;
iph->tot_len = htons(sizeof(struct iphdr)
+ sizeof(struct icmphdr)
+ payload_length);
get_random_bytes(&iph->id, sizeof(iph->id));
iph->frag_off = 0;
iph->ttl = IPDEFTTL;
iph->protocol = IPPROTO_ICMP;
iph->daddr = old_iph->saddr;
iph->saddr = old_iph->daddr;

ip_send_check(iph);

/* ICMP */
icmph->type = ICMP_DEST_UNREACH;
icmph->code = ICMP_FRAG_NEEDED;
icmph->un.gateway = htonl(mtu);
icmph->checksum = 0;

nskb->csum = csum_partial((u8 *)icmph, sizeof(struct icmphdr), 0);
nskb->csum = skb_copy_and_csum_bits(skb, (u8 *)old_iph - skb->data,
payload, payload_length,
nskb->csum);
icmph->checksum = csum_fold(nskb->csum);
}

#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
static bool ipv6_should_icmp(struct sk_buff *skb)
{
struct ipv6hdr *old_ipv6h = ipv6_hdr(skb);
int addr_type;
int payload_off = (u8 *)(old_ipv6h + 1) - skb->data;
u8 nexthdr = ipv6_hdr(skb)->nexthdr;
__be16 frag_off;

/* Check source address is valid. */
addr_type = ipv6_addr_type(&old_ipv6h->saddr);
if (addr_type & IPV6_ADDR_MULTICAST || addr_type == IPV6_ADDR_ANY)
return false;

/* Don't reply to unspecified addresses. */
if (ipv6_addr_type(&old_ipv6h->daddr) == IPV6_ADDR_ANY)
return false;

/* Don't respond to ICMP error messages. */
payload_off = ipv6_skip_exthdr(skb, payload_off, &nexthdr, &frag_off);
if (payload_off < 0)
return false;

if (nexthdr == NEXTHDR_ICMP) {
u8 icmp_type, *icmp_typep;

icmp_typep = skb_header_pointer(skb, payload_off +
offsetof(struct icmp6hdr,
icmp6_type),
sizeof(icmp_type), &icmp_type);

if (!icmp_typep || !(*icmp_typep & ICMPV6_INFOMSG_MASK))
return false;
}

return true;
}

static void ipv6_build_icmp(struct sk_buff *skb, struct sk_buff *nskb,
unsigned int mtu, unsigned int payload_length)
{
struct ipv6hdr *ipv6h, *old_ipv6h = ipv6_hdr(skb);
struct icmp6hdr *icmp6h;
u8 *payload;

ipv6h = (struct ipv6hdr *)skb_put(nskb, sizeof(struct ipv6hdr));
icmp6h = (struct icmp6hdr *)skb_put(nskb, sizeof(struct icmp6hdr));
payload = skb_put(nskb, payload_length);

/* IPv6 */
ipv6h->version = 6;
ipv6h->priority = 0;
memset(&ipv6h->flow_lbl, 0, sizeof(ipv6h->flow_lbl));
ipv6h->payload_len = htons(sizeof(struct icmp6hdr)
+ payload_length);
ipv6h->nexthdr = NEXTHDR_ICMP;
ipv6h->hop_limit = IPV6_DEFAULT_HOPLIMIT;
ipv6h->daddr = old_ipv6h->saddr;
ipv6h->saddr = old_ipv6h->daddr;

/* ICMPv6 */
icmp6h->icmp6_type = ICMPV6_PKT_TOOBIG;
icmp6h->icmp6_code = 0;
icmp6h->icmp6_cksum = 0;
icmp6h->icmp6_mtu = htonl(mtu);

nskb->csum = csum_partial((u8 *)icmp6h, sizeof(struct icmp6hdr), 0);
nskb->csum = skb_copy_and_csum_bits(skb, (u8 *)old_ipv6h - skb->data,
payload, payload_length,
nskb->csum);
icmp6h->icmp6_cksum = csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
sizeof(struct icmp6hdr)
+ payload_length,
ipv6h->nexthdr, nskb->csum);
}
#endif /* IPv6 */

bool ovs_tnl_frag_needed(struct vport *vport,
const struct tnl_mutable_config *mutable,
struct sk_buff *skb, unsigned int mtu)
{
unsigned int eth_hdr_len = ETH_HLEN;
unsigned int total_length = 0, header_length = 0, payload_length;
struct ethhdr *eh, *old_eh = eth_hdr(skb);
struct sk_buff *nskb;

/* Sanity check */
if (skb->protocol == htons(ETH_P_IP)) {
if (mtu < IP_MIN_MTU)
return false;

if (!ipv4_should_icmp(skb))
return true;
}
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
else if (skb->protocol == htons(ETH_P_IPV6)) {
if (mtu < IPV6_MIN_MTU)
return false;

/*
* In theory we should do PMTUD on IPv6 multicast messages but
* we don't have an address to send from so just fragment.
*/
if (ipv6_addr_type(&ipv6_hdr(skb)->daddr) & IPV6_ADDR_MULTICAST)
return false;

if (!ipv6_should_icmp(skb))
return true;
}
#endif
else
return false;

/* Allocate */
if (old_eh->h_proto == htons(ETH_P_8021Q))
eth_hdr_len = VLAN_ETH_HLEN;

payload_length = skb->len - eth_hdr_len;
if (skb->protocol == htons(ETH_P_IP)) {
header_length = sizeof(struct iphdr) + sizeof(struct icmphdr);
total_length = min_t(unsigned int, header_length +
payload_length, 576);
}
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
else {
header_length = sizeof(struct ipv6hdr) +
sizeof(struct icmp6hdr);
total_length = min_t(unsigned int, header_length +
payload_length, IPV6_MIN_MTU);
}
#endif

payload_length = total_length - header_length;

nskb = dev_alloc_skb(NET_IP_ALIGN + eth_hdr_len + header_length +
payload_length);
if (!nskb)
return false;

skb_reserve(nskb, NET_IP_ALIGN);

/* Ethernet / VLAN */
eh = (struct ethhdr *)skb_put(nskb, eth_hdr_len);
memcpy(eh->h_dest, old_eh->h_source, ETH_ALEN);
memcpy(eh->h_source, mutable->eth_addr, ETH_ALEN);
nskb->protocol = eh->h_proto = old_eh->h_proto;
if (old_eh->h_proto == htons(ETH_P_8021Q)) {
struct vlan_ethhdr *vh = (struct vlan_ethhdr *)eh;

vh->h_vlan_TCI = vlan_eth_hdr(skb)->h_vlan_TCI;
vh->h_vlan_encapsulated_proto = skb->protocol;
} else
vlan_set_tci(nskb, vlan_get_tci(skb));
skb_reset_mac_header(nskb);

/* Protocol */
if (skb->protocol == htons(ETH_P_IP))
ipv4_build_icmp(skb, nskb, mtu, payload_length);
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
else
ipv6_build_icmp(skb, nskb, mtu, payload_length);
#endif

if (unlikely(compute_ip_summed(nskb, false))) {
kfree_skb(nskb);
return false;
}

ovs_vport_receive(vport, nskb);

return true;
}

static bool check_mtu(struct sk_buff *skb,
struct vport *vport,
const struct tnl_mutable_config *mutable,
const struct rtable *rt, __be16 *frag_offp,
int tunnel_hlen)
{
bool pmtud;
__be16 frag_off;
int mtu = 0;
unsigned int packet_length = skb->len - ETH_HLEN;

if (OVS_CB(skb)->tun_key->ipv4_dst) {
pmtud = false;
frag_off = OVS_CB(skb)->tun_key->tun_flags & OVS_TNL_F_DONT_FRAGMENT ?
htons(IP_DF) : 0;
} else {
pmtud = mutable->flags & TNL_F_PMTUD;
frag_off = mutable->flags & TNL_F_DF_DEFAULT ? htons(IP_DF) : 0;
}

/* Allow for one level of tagging in the packet length. */
if (!vlan_tx_tag_present(skb) &&
eth_hdr(skb)->h_proto == htons(ETH_P_8021Q))
packet_length -= VLAN_HLEN;

if (pmtud) {
int vlan_header = 0;

/* The tag needs to go in packet regardless of where it
* currently is, so subtract it from the MTU.
*/
if (vlan_tx_tag_present(skb) ||
eth_hdr(skb)->h_proto == htons(ETH_P_8021Q))
vlan_header = VLAN_HLEN;

mtu = dst_mtu(&rt_dst(rt))
- ETH_HLEN
- tunnel_hlen
- vlan_header;
}

if (skb->protocol == htons(ETH_P_IP)) {
struct iphdr *iph = ip_hdr(skb);

if (pmtud && iph->frag_off & htons(IP_DF)) {
mtu = max(mtu, IP_MIN_MTU);

if (packet_length > mtu &&
ovs_tnl_frag_needed(vport, mutable, skb, mtu))
return false;
}
}
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
else if (skb->protocol == htons(ETH_P_IPV6)) {
/* IPv6 requires end hosts to do fragmentation
* if the packet is above the minimum MTU.
*/
if (packet_length > IPV6_MIN_MTU)
frag_off = htons(IP_DF);

if (pmtud) {
mtu = max(mtu, IPV6_MIN_MTU);

if (packet_length > mtu &&
ovs_tnl_frag_needed(vport, mutable, skb, mtu))
return false;
}
}
#endif

*frag_offp = frag_off;
return true;
}

static struct rtable *find_route(struct net *net,
__be32 *saddr, __be32 daddr, u8 ipproto,
u8 tos)
Expand Down Expand Up @@ -850,7 +513,7 @@ int ovs_tnl_send(struct vport *vport, struct sk_buff *skb)
struct ovs_key_ipv4_tunnel tun_key;
int sent_len = 0;
int tunnel_hlen;
__be16 frag_off = 0;
__be16 frag_off;
__be32 daddr;
__be32 saddr;
u8 ttl;
Expand Down Expand Up @@ -899,6 +562,8 @@ int ovs_tnl_send(struct vport *vport, struct sk_buff *skb)
saddr = OVS_CB(skb)->tun_key->ipv4_src;
tos = OVS_CB(skb)->tun_key->ipv4_tos;
ttl = OVS_CB(skb)->tun_key->ipv4_ttl;
frag_off = OVS_CB(skb)->tun_key->tun_flags &
OVS_TNL_F_DONT_FRAGMENT ? htons(IP_DF) : 0;
} else {
u8 inner_tos;
daddr = mutable->key.daddr;
Expand Down Expand Up @@ -939,6 +604,7 @@ int ovs_tnl_send(struct vport *vport, struct sk_buff *skb)
#endif
}

frag_off = mutable->flags & TNL_F_DF_DEFAULT ? htons(IP_DF) : 0;
}

/* Route lookup */
Expand All @@ -960,12 +626,6 @@ int ovs_tnl_send(struct vport *vport, struct sk_buff *skb)
goto err_free_rt;
}

/* MTU */
if (unlikely(!check_mtu(skb, vport, mutable, rt, &frag_off, tunnel_hlen))) {
err = VPORT_E_TX_DROPPED;
goto err_free_rt;
}

/* TTL Fixup. */
if (!OVS_CB(skb)->tun_key->ipv4_dst) {
if (!(mutable->flags & TNL_F_TTL_INHERIT)) {
Expand Down
2 changes: 1 addition & 1 deletion datapath/tunnel.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,7 +56,7 @@

/* All public tunnel flags. */
#define TNL_F_PUBLIC (TNL_F_CSUM | TNL_F_TOS_INHERIT | TNL_F_TTL_INHERIT | \
TNL_F_DF_DEFAULT | TNL_F_PMTUD | TNL_F_IPSEC)
TNL_F_DF_DEFAULT | TNL_F_IPSEC)

/**
* struct port_lookup_key - Tunnel port key, used as hash table key.
Expand Down
Loading

0 comments on commit 78adaee

Please sign in to comment.