udpv4: Handle large incoming UDP/IPv4 packets and support software UFO.

- validate and forward GSO UDP/IPv4 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>

2 files changed, 72 insertions, 1 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 566ea6c4321d..197d024b2536 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1187,6 +1187,7 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb, int features)
         int proto;
         int ihl;
         int id;
+        unsigned int offset = 0;
 
         if (!(features & NETIF_F_V4_CSUM))
                 features &= ~NETIF_F_SG;
@@ -1229,7 +1230,14 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb, int features)
         skb = segs;
         do {
                 iph = ip_hdr(skb);
-                iph->id = htons(id++);
+                if (proto == IPPROTO_UDP) {
+                        iph->id = htons(id);
+                        iph->frag_off = htons(offset >> 3);
+                        if (skb->next != NULL)
+                                iph->frag_off |= htons(IP_MF);
+                        offset += (skb->len - skb->mac_len - iph->ihl * 4);
+                } else
+                        iph->id = htons(id++);
                 iph->tot_len = htons(skb->len - skb->mac_len);
                 iph->check = 0;
                 iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
@@ -1425,6 +1433,8 @@ static struct net_protocol tcp_protocol = {
 static struct net_protocol udp_protocol = {
         .handler =      udp_rcv,
         .err_handler =  udp_err,
+        .gso_send_check = udp4_ufo_send_check,
+        .gso_segment = udp4_ufo_fragment,
         .no_policy =    1,
         .netns_ok =     1,
 };
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 80e3812837ad..7bc2d082a49e 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1816,6 +1816,67 @@ void __init udp_init(void)
         sysctl_udp_wmem_min = SK_MEM_QUANTUM;
 }
 
+int udp4_ufo_send_check(struct sk_buff *skb)
+{
+        const struct iphdr *iph;
+        struct udphdr *uh;
+
+        if (!pskb_may_pull(skb, sizeof(*uh)))
+                return -EINVAL;
+
+        iph = ip_hdr(skb);
+        uh = udp_hdr(skb);
+
+        uh->check = ~csum_tcpudp_magic(iph->saddr, iph->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;
+}
+
+struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, int features)
+{
+        struct sk_buff *segs = ERR_PTR(-EINVAL);
+        unsigned int mss;
+        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;
+
+        /* Fragment the skb. IP headers of the fragments are updated in
+         * inet_gso_segment()
+         */
+        segs = skb_segment(skb, features);
+out:
+        return segs;
+}
+
 EXPORT_SYMBOL(udp_disconnect);
 EXPORT_SYMBOL(udp_ioctl);
 EXPORT_SYMBOL(udp_prot);