From 6623e3b24a5ebb07e81648c478d286a1329ab891 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 5 Jan 2011 07:52:55 +0000 Subject: [PATCH] ipv4: IP defragmentation must be ECN aware RFC3168 (The Addition of Explicit Congestion Notification to IP) states : 5.3. Fragmentation ECN-capable packets MAY have the DF (Don't Fragment) bit set. Reassembly of a fragmented packet MUST NOT lose indications of congestion. In other words, if any fragment of an IP packet to be reassembled has the CE codepoint set, then one of two actions MUST be taken: * Set the CE codepoint on the reassembled packet. However, this MUST NOT occur if any of the other fragments contributing to this reassembly carries the Not-ECT codepoint. * The packet is dropped, instead of being reassembled, for any other reason. This patch implements this requirement for IPv4, choosing the first action : If one fragment had NO-ECT codepoint reassembled frame has NO-ECT ElIf one fragment had CE codepoint reassembled frame has CE Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_fragment.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index e6215bdd96c0..a1151b8adf3c 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -45,6 +45,7 @@ #include #include #include +#include /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c @@ -70,11 +71,28 @@ struct ipq { __be32 daddr; __be16 id; u8 protocol; + u8 ecn; /* RFC3168 support */ int iif; unsigned int rid; struct inet_peer *peer; }; +#define IPFRAG_ECN_CLEAR 0x01 /* one frag had INET_ECN_NOT_ECT */ +#define IPFRAG_ECN_SET_CE 0x04 /* one frag had INET_ECN_CE */ + +static inline u8 ip4_frag_ecn(u8 tos) +{ + tos = (tos & INET_ECN_MASK) + 1; + /* + * After the last operation we have (in binary): + * INET_ECN_NOT_ECT => 001 + * INET_ECN_ECT_1 => 010 + * INET_ECN_ECT_0 => 011 + * INET_ECN_CE => 100 + */ + return (tos & 2) ? 0 : tos; +} + static struct inet_frags ip4_frags; int ip_frag_nqueues(struct net *net) @@ -137,6 +155,7 @@ static void ip4_frag_init(struct inet_frag_queue *q, void *a) qp->protocol = arg->iph->protocol; qp->id = arg->iph->id; + qp->ecn = ip4_frag_ecn(arg->iph->tos); qp->saddr = arg->iph->saddr; qp->daddr = arg->iph->daddr; qp->user = arg->user; @@ -316,6 +335,7 @@ static int ip_frag_reinit(struct ipq *qp) qp->q.fragments = NULL; qp->q.fragments_tail = NULL; qp->iif = 0; + qp->ecn = 0; return 0; } @@ -328,6 +348,7 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) int flags, offset; int ihl, end; int err = -ENOENT; + u8 ecn; if (qp->q.last_in & INET_FRAG_COMPLETE) goto err; @@ -339,6 +360,7 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) goto err; } + ecn = ip4_frag_ecn(ip_hdr(skb)->tos); offset = ntohs(ip_hdr(skb)->frag_off); flags = offset & ~IP_OFFSET; offset &= IP_OFFSET; @@ -472,6 +494,7 @@ found: } qp->q.stamp = skb->tstamp; qp->q.meat += skb->len; + qp->ecn |= ecn; atomic_add(skb->truesize, &qp->q.net->mem); if (offset == 0) qp->q.last_in |= INET_FRAG_FIRST_IN; @@ -583,6 +606,17 @@ static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev, iph = ip_hdr(head); iph->frag_off = 0; iph->tot_len = htons(len); + /* RFC3168 5.3 Fragmentation support + * If one fragment had INET_ECN_NOT_ECT, + * reassembled frame also has INET_ECN_NOT_ECT + * Elif one fragment had INET_ECN_CE + * reassembled frame also has INET_ECN_CE + */ + if (qp->ecn & IPFRAG_ECN_CLEAR) + iph->tos &= ~INET_ECN_MASK; + else if (qp->ecn & IPFRAG_ECN_SET_CE) + iph->tos |= INET_ECN_CE; + IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS); qp->q.fragments = NULL; qp->q.fragments_tail = NULL; -- 2.39.5