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Subject[PATCH 5.3 120/140] ipv4: fix IPSKB_FRAG_PMTU handling with fragmentation
Date
From: Eric Dumazet <edumazet@google.com>

[ Upstream commit e7a409c3f46cb0dbc7bfd4f6f9421d53e92614a5 ]

This patch removes the iph field from the state structure, which is not
properly initialized. Instead, add a new field to make the "do we want
to set DF" be the state bit and move the code to set the DF flag from
ip_frag_next().

Joint work with Pablo and Linus.

Fixes: 19c3401a917b ("net: ipv4: place control buffer handling away from fragmentation iterators")
Reported-by: Patrick Schönthaler <patrick@notvads.ovh>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/ip.h | 4 ++--
net/bridge/netfilter/nf_conntrack_bridge.c | 2 +-
net/ipv4/ip_output.c | 11 ++++++-----
3 files changed, 9 insertions(+), 8 deletions(-)

--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -184,7 +184,7 @@ static inline struct sk_buff *ip_fraglis
}

struct ip_frag_state {
- struct iphdr *iph;
+ bool DF;
unsigned int hlen;
unsigned int ll_rs;
unsigned int mtu;
@@ -195,7 +195,7 @@ struct ip_frag_state {
};

void ip_frag_init(struct sk_buff *skb, unsigned int hlen, unsigned int ll_rs,
- unsigned int mtu, struct ip_frag_state *state);
+ unsigned int mtu, bool DF, struct ip_frag_state *state);
struct sk_buff *ip_frag_next(struct sk_buff *skb,
struct ip_frag_state *state);

--- a/net/bridge/netfilter/nf_conntrack_bridge.c
+++ b/net/bridge/netfilter/nf_conntrack_bridge.c
@@ -94,7 +94,7 @@ slow_path:
* This may also be a clone skbuff, we could preserve the geometry for
* the copies but probably not worth the effort.
*/
- ip_frag_init(skb, hlen, ll_rs, frag_max_size, &state);
+ ip_frag_init(skb, hlen, ll_rs, frag_max_size, false, &state);

while (state.left > 0) {
struct sk_buff *skb2;
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -645,11 +645,12 @@ void ip_fraglist_prepare(struct sk_buff
EXPORT_SYMBOL(ip_fraglist_prepare);

void ip_frag_init(struct sk_buff *skb, unsigned int hlen,
- unsigned int ll_rs, unsigned int mtu,
+ unsigned int ll_rs, unsigned int mtu, bool DF,
struct ip_frag_state *state)
{
struct iphdr *iph = ip_hdr(skb);

+ state->DF = DF;
state->hlen = hlen;
state->ll_rs = ll_rs;
state->mtu = mtu;
@@ -668,9 +669,6 @@ static void ip_frag_ipcb(struct sk_buff
/* Copy the flags to each fragment. */
IPCB(to)->flags = IPCB(from)->flags;

- if (IPCB(from)->flags & IPSKB_FRAG_PMTU)
- state->iph->frag_off |= htons(IP_DF);
-
/* ANK: dirty, but effective trick. Upgrade options only if
* the segment to be fragmented was THE FIRST (otherwise,
* options are already fixed) and make it ONCE
@@ -738,6 +736,8 @@ struct sk_buff *ip_frag_next(struct sk_b
*/
iph = ip_hdr(skb2);
iph->frag_off = htons((state->offset >> 3));
+ if (state->DF)
+ iph->frag_off |= htons(IP_DF);

/*
* Added AC : If we are fragmenting a fragment that's not the
@@ -881,7 +881,8 @@ slow_path:
* Fragment the datagram.
*/

- ip_frag_init(skb, hlen, ll_rs, mtu, &state);
+ ip_frag_init(skb, hlen, ll_rs, mtu, IPCB(skb)->flags & IPSKB_FRAG_PMTU,
+ &state);

/*
* Keep copying data until we run out.

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