udpv6: Handle large incoming UDP/IPv6 packets and support software UFO

- validate and forward GSO UDP/IPv6 packets from untrusted sources.
- do software UFO if the outgoing device doesn't support UFO.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 93 insertions, 0 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index f31b1b9b0e0e..d79fa6724451 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1078,9 +1078,102 @@ int compat_udpv6_getsockopt(struct sock *sk, int level, int optname,
 }
 #endif
 
+static int udp6_ufo_send_check(struct sk_buff *skb)
+{
+        struct ipv6hdr *ipv6h;
+        struct udphdr *uh;
+
+        if (!pskb_may_pull(skb, sizeof(*uh)))
+                return -EINVAL;
+
+        ipv6h = ipv6_hdr(skb);
+        uh = udp_hdr(skb);
+
+        uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
+                                     IPPROTO_UDP, 0);
+        skb->csum_start = skb_transport_header(skb) - skb->head;
+        skb->csum_offset = offsetof(struct udphdr, check);
+        skb->ip_summed = CHECKSUM_PARTIAL;
+        return 0;
+}
+
+static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, int features)
+{
+        struct sk_buff *segs = ERR_PTR(-EINVAL);
+        unsigned int mss;
+        unsigned int unfrag_ip6hlen, unfrag_len;
+        struct frag_hdr *fptr;
+        u8 *mac_start, *prevhdr;
+        u8 nexthdr;
+        u8 frag_hdr_sz = sizeof(struct frag_hdr);
+        int offset;
+        __wsum csum;
+
+        mss = skb_shinfo(skb)->gso_size;
+        if (unlikely(skb->len <= mss))
+                goto out;
+
+        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
+                /* Packet is from an untrusted source, reset gso_segs. */
+                int type = skb_shinfo(skb)->gso_type;
+
+                if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY) ||
+                             !(type & (SKB_GSO_UDP))))
+                        goto out;
+
+                skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
+
+                segs = NULL;
+                goto out;
+        }
+
+        /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
+         * do checksum of UDP packets sent as multiple IP fragments.
+         */
+        offset = skb->csum_start - skb_headroom(skb);
+        csum = skb_checksum(skb, offset, skb->len- offset, 0);
+        offset += skb->csum_offset;
+        *(__sum16 *)(skb->data + offset) = csum_fold(csum);
+        skb->ip_summed = CHECKSUM_NONE;
+
+        /* Check if there is enough headroom to insert fragment header. */
+        if ((skb_headroom(skb) < frag_hdr_sz) &&
+            pskb_expand_head(skb, frag_hdr_sz, 0, GFP_ATOMIC))
+                goto out;
+
+        /* Find the unfragmentable header and shift it left by frag_hdr_sz
+         * bytes to insert fragment header.
+         */
+        unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
+        nexthdr = *prevhdr;
+        *prevhdr = NEXTHDR_FRAGMENT;
+        unfrag_len = skb_network_header(skb) - skb_mac_header(skb) +
+                     unfrag_ip6hlen;
+        mac_start = skb_mac_header(skb);
+        memmove(mac_start-frag_hdr_sz, mac_start, unfrag_len);
+
+        skb->mac_header -= frag_hdr_sz;
+        skb->network_header -= frag_hdr_sz;
+
+        fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
+        fptr->nexthdr = nexthdr;
+        fptr->reserved = 0;
+        ipv6_select_ident(fptr);
+
+        /* Fragment the skb. ipv6 header and the remaining fields of the
+         * fragment header are updated in ipv6_gso_segment()
+         */
+        segs = skb_segment(skb, features);
+
+out:
+        return segs;
+}
+
 static struct inet6_protocol udpv6_protocol = {
         .handler        =       udpv6_rcv,
         .err_handler    =       udpv6_err,
+        .gso_send_check =       udp6_ufo_send_check,
+        .gso_segment    =       udp6_ufo_fragment,
         .flags          =       INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
 };