Message ID | 1440636965-11552-1-git-send-email-chenweilong@huawei.com |
---|---|
State | Rejected, archived |
Delegated to: | David Miller |
Headers | show |
On Thu, 2015-08-27 at 08:56 +0800, chenweilong@huawei.com wrote: > From: Weilong Chen <chenweilong@huawei.com> > > When try to merge several skbs to prior one, if the frag_list is > used and the the last one is a small packet, once the condition > "len <= skb_tailroom(to)" is satisfied, we will get a wrong > packet! > This patch just check frag_lists before the condtion to prevent > this from happening. > > Signed-off-by: Weilong Chen <chenweilong@huawei.com> > --- > net/core/skbuff.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index 8a725cc..d08edcb 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > if (skb_cloned(to)) > return false; > > + if (skb_has_frag_list(to) || skb_has_frag_list(from)) > + return false; > + > if (len <= skb_tailroom(to)) { > if (len) > BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); > @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > return true; > } > > - if (skb_has_frag_list(to) || skb_has_frag_list(from)) > - return false; > - > if (skb_headlen(from) != 0) { > struct page *page; > unsigned int offset; Sigh. No idea what problem you tried to solve. This patch is not needed. If (len <= skb_tailroom()), then it is obviously correct to copy_bits() the bytes. Hints : - If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not be done. - If @from has a fraglist, it is not relevant as we copy it into @to and will free @from. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, 2015-08-26 at 19:12 -0700, Eric Dumazet wrote: > On Thu, 2015-08-27 at 08:56 +0800, chenweilong@huawei.com wrote: > > From: Weilong Chen <chenweilong@huawei.com> > > > > When try to merge several skbs to prior one, if the frag_list is > > used and the the last one is a small packet, once the condition > > "len <= skb_tailroom(to)" is satisfied, we will get a wrong > > packet! > > This patch just check frag_lists before the condtion to prevent > > this from happening. > > > > Signed-off-by: Weilong Chen <chenweilong@huawei.com> > > --- > > net/core/skbuff.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index 8a725cc..d08edcb 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > > if (skb_cloned(to)) > > return false; > > > > + if (skb_has_frag_list(to) || skb_has_frag_list(from)) > > + return false; > > + > > if (len <= skb_tailroom(to)) { > > if (len) > > BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); > > @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > > return true; > > } > > > > - if (skb_has_frag_list(to) || skb_has_frag_list(from)) > > - return false; > > - > > if (skb_headlen(from) != 0) { > > struct page *page; > > unsigned int offset; > > Sigh. > > No idea what problem you tried to solve. > > This patch is not needed. > > If (len <= skb_tailroom()), then it is obviously correct to copy_bits() > the bytes. > > Hints : > > - If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not > be done. > > - If @from has a fraglist, it is not relevant as we copy it into @to and > will free @from. This is going to be a FAQ http://www.spinics.net/lists/netdev/msg315090.html -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Thanks for reply. > On Wed, 2015-08-26 at 19:12 -0700, Eric Dumazet wrote: >> On Thu, 2015-08-27 at 08:56 +0800, chenweilong@huawei.com wrote: >>> From: Weilong Chen <chenweilong@huawei.com> >>> >>> When try to merge several skbs to prior one, if the frag_list is >>> used and the the last one is a small packet, once the condition >>> "len <= skb_tailroom(to)" is satisfied, we will get a wrong >>> packet! >>> This patch just check frag_lists before the condtion to prevent >>> this from happening. >>> >>> Signed-off-by: Weilong Chen <chenweilong@huawei.com> >>> --- >>> net/core/skbuff.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c >>> index 8a725cc..d08edcb 100644 >>> --- a/net/core/skbuff.c >>> +++ b/net/core/skbuff.c >>> @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, >>> if (skb_cloned(to)) >>> return false; >>> >>> + if (skb_has_frag_list(to) || skb_has_frag_list(from)) >>> + return false; >>> + >>> if (len <= skb_tailroom(to)) { >>> if (len) >>> BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); >>> @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, >>> return true; >>> } >>> >>> - if (skb_has_frag_list(to) || skb_has_frag_list(from)) >>> - return false; >>> - >>> if (skb_headlen(from) != 0) { >>> struct page *page; >>> unsigned int offset; >> >> Sigh. >> >> No idea what problem you tried to solve. >> >> This patch is not needed. >> >> If (len <= skb_tailroom()), then it is obviously correct to copy_bits() >> the bytes. >> >> Hints : >> >> - If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not >> be done. How to make sure it? In my test, @to has a fraglist, but skb_tailroom(to) is not 0! The test is about tipc, the function tipc_buf_append will merge 3 skbs to one: packet 1: len = 1420 skb_tailroom = 190 packet 2: len = 1420 packet 2 will be add to 1' fraglist, but not update skb_tailroom packet 3: len = 60 Here's the error! >> >> - If @from has a fraglist, it is not relevant as we copy it into @to and >> will free @from. > > This is going to be a FAQ > > http://www.spinics.net/lists/netdev/msg315090.html > > > > > > . > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Weilong Chen <chenweilong@huawei.com> Date: Fri, 28 Aug 2015 11:35:40 +0800 > In my test, @to has a fraglist, but skb_tailroom(to) is not 0! > The test is about tipc, the function tipc_buf_append will merge 3 skbs > to one: > packet 1: len = 1420 skb_tailroom = 190 > packet 2: len = 1420 > packet 2 will be add to 1' fraglist, but not update skb_tailroom This operation is illegal. Once there are frags, tailroom is not permitted. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 2015-08-28 at 11:35 +0800, Weilong Chen wrote: > Thanks for reply. > > > On Wed, 2015-08-26 at 19:12 -0700, Eric Dumazet wrote: > >> On Thu, 2015-08-27 at 08:56 +0800, chenweilong@huawei.com wrote: > >>> From: Weilong Chen <chenweilong@huawei.com> > >>> > >>> When try to merge several skbs to prior one, if the frag_list is > >>> used and the the last one is a small packet, once the condition > >>> "len <= skb_tailroom(to)" is satisfied, we will get a wrong > >>> packet! > >>> This patch just check frag_lists before the condtion to prevent > >>> this from happening. > >>> > >>> Signed-off-by: Weilong Chen <chenweilong@huawei.com> > >>> --- > >>> net/core/skbuff.c | 6 +++--- > >>> 1 file changed, 3 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c > >>> index 8a725cc..d08edcb 100644 > >>> --- a/net/core/skbuff.c > >>> +++ b/net/core/skbuff.c > >>> @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > >>> if (skb_cloned(to)) > >>> return false; > >>> > >>> + if (skb_has_frag_list(to) || skb_has_frag_list(from)) > >>> + return false; > >>> + > >>> if (len <= skb_tailroom(to)) { > >>> if (len) > >>> BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); > >>> @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, > >>> return true; > >>> } > >>> > >>> - if (skb_has_frag_list(to) || skb_has_frag_list(from)) > >>> - return false; > >>> - > >>> if (skb_headlen(from) != 0) { > >>> struct page *page; > >>> unsigned int offset; > >> > >> Sigh. > >> > >> No idea what problem you tried to solve. > >> > >> This patch is not needed. > >> > >> If (len <= skb_tailroom()), then it is obviously correct to copy_bits() > >> the bytes. > >> > >> Hints : > >> > >> - If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not > >> be done. > > How to make sure it? > In my test, @to has a fraglist, but skb_tailroom(to) is not 0! > The test is about tipc, the function tipc_buf_append will merge 3 skbs > to one: > packet 1: len = 1420 skb_tailroom = 190 > packet 2: len = 1420 > packet 2 will be add to 1' fraglist, but not update skb_tailroom > packet 3: len = 60 > Here's the error! Then fix tipc, or make sure you read and understood the code. By definition, if one skb has something in fraglist, it is non linear. If you read skb_tailroom(), you'll see this function returns 0 if skb is non linear. include/linux/skbuff.h-/** include/linux/skbuff.h: * skb_tailroom - bytes at buffer end include/linux/skbuff.h- * @skb: buffer to check include/linux/skbuff.h- * include/linux/skbuff.h- * Return the number of bytes of free space at the tail of an sk_buff include/linux/skbuff.h- */ include/linux/skbuff.h:static inline int skb_tailroom(const struct sk_buff *skb) include/linux/skbuff.h-{ include/linux/skbuff.h- return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail; include/linux/skbuff.h-} -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
在 2015/8/28 12:37, Eric Dumazet 写道: > On Fri, 2015-08-28 at 11:35 +0800, Weilong Chen wrote: >> Thanks for reply. >> >>> On Wed, 2015-08-26 at 19:12 -0700, Eric Dumazet wrote: >>>> On Thu, 2015-08-27 at 08:56 +0800, chenweilong@huawei.com wrote: >>>>> From: Weilong Chen <chenweilong@huawei.com> >>>>> >>>>> When try to merge several skbs to prior one, if the frag_list is >>>>> used and the the last one is a small packet, once the condition >>>>> "len <= skb_tailroom(to)" is satisfied, we will get a wrong >>>>> packet! >>>>> This patch just check frag_lists before the condtion to prevent >>>>> this from happening. >>>>> >>>>> Signed-off-by: Weilong Chen <chenweilong@huawei.com> >>>>> --- >>>>> net/core/skbuff.c | 6 +++--- >>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>> >>>>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c >>>>> index 8a725cc..d08edcb 100644 >>>>> --- a/net/core/skbuff.c >>>>> +++ b/net/core/skbuff.c >>>>> @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, >>>>> if (skb_cloned(to)) >>>>> return false; >>>>> >>>>> + if (skb_has_frag_list(to) || skb_has_frag_list(from)) >>>>> + return false; >>>>> + >>>>> if (len <= skb_tailroom(to)) { >>>>> if (len) >>>>> BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); >>>>> @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, >>>>> return true; >>>>> } >>>>> >>>>> - if (skb_has_frag_list(to) || skb_has_frag_list(from)) >>>>> - return false; >>>>> - >>>>> if (skb_headlen(from) != 0) { >>>>> struct page *page; >>>>> unsigned int offset; >>>> >>>> Sigh. >>>> >>>> No idea what problem you tried to solve. >>>> >>>> This patch is not needed. >>>> >>>> If (len <= skb_tailroom()), then it is obviously correct to copy_bits() >>>> the bytes. >>>> >>>> Hints : >>>> >>>> - If @to has a fraglist, then skb_tailroom(to) is 0 so the copy can not >>>> be done. >> >> How to make sure it? >> In my test, @to has a fraglist, but skb_tailroom(to) is not 0! >> The test is about tipc, the function tipc_buf_append will merge 3 skbs >> to one: >> packet 1: len = 1420 skb_tailroom = 190 >> packet 2: len = 1420 >> packet 2 will be add to 1' fraglist, but not update skb_tailroom >> packet 3: len = 60 >> Here's the error! > > Then fix tipc, or make sure you read and understood the code. > > By definition, if one skb has something in fraglist, it is non linear. > > If you read skb_tailroom(), you'll see this function returns 0 if skb is > non linear. Yes you'er right, when packet 2 is add to 1' fraglist, tipc should update the packet 1' 'len' and 'data_len'. In my kernel(v3.10), it doesn't do that, which was corrected in commit 5074a (v3.16). Thanks for your patience > > include/linux/skbuff.h-/** > include/linux/skbuff.h: * skb_tailroom - bytes at buffer end > include/linux/skbuff.h- * @skb: buffer to check > include/linux/skbuff.h- * > include/linux/skbuff.h- * Return the number of bytes of free space at the tail of an sk_buff > include/linux/skbuff.h- */ > include/linux/skbuff.h:static inline int skb_tailroom(const struct sk_buff *skb) > include/linux/skbuff.h-{ > include/linux/skbuff.h- return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail; > include/linux/skbuff.h-} > > > > > . > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> From: Weilong Chen <chenweilong@huawei.com> > Date: Fri, 28 Aug 2015 11:35:40 +0800 > >> In my test, @to has a fraglist, but skb_tailroom(to) is not 0! >> The test is about tipc, the function tipc_buf_append will merge 3 skbs >> to one: >> packet 1: len = 1420 skb_tailroom = 190 >> packet 2: len = 1420 >> packet 2 will be add to 1' fraglist, but not update skb_tailroom > > This operation is illegal. > > Once there are frags, tailroom is not permitted. > > . > Agree Thanks -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 8a725cc..d08edcb 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4133,6 +4133,9 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, if (skb_cloned(to)) return false; + if (skb_has_frag_list(to) || skb_has_frag_list(from)) + return false; + if (len <= skb_tailroom(to)) { if (len) BUG_ON(skb_copy_bits(from, 0, skb_put(to, len), len)); @@ -4140,9 +4143,6 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from, return true; } - if (skb_has_frag_list(to) || skb_has_frag_list(from)) - return false; - if (skb_headlen(from) != 0) { struct page *page; unsigned int offset;