Re: [PATCH v2 net] net: udp: fix Fast/frag0 UDP GRO
From: Alexander Lobakin <hidden>
Date: 2020-11-09 19:56:40
Also in:
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From: Eric Dumazet <redacted> Date: Mon, 9 Nov 2020 20:29:03 +0100
On 11/9/20 7:26 PM, Alexander Lobakin wrote:quoted
From: Eric Dumazet <redacted> Date: Mon, 9 Nov 2020 18:37:36 +0100quoted
On 11/9/20 5:56 PM, Alexander Lobakin wrote:quoted
While testing UDP GSO fraglists forwarding through driver that uses Fast GRO (via napi_gro_frags()), I was observing lots of out-of-order iperf packets:.quoted
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Since v1 [1]: - added a NULL pointer check for "uh" as suggested by Willem. [1] https://lore.kernel.org/netdev/YazU6GEzBdpyZMDMwJirxDX7B4sualpDG68ADZYvJI@cp4-web-034.plabs.ch (local) Fixes: e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.") Signed-off-by: Alexander Lobakin <redacted> --- net/ipv4/udp_offload.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index e67a66fbf27b..7f6bd221880a 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c@@ -366,13 +366,18 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb, static struct sk_buff *udp_gro_receive_segment(struct list_head *head, struct sk_buff *skb) { - struct udphdr *uh = udp_hdr(skb); + struct udphdr *uh = udp_gro_udphdr(skb); struct sk_buff *pp = NULL; struct udphdr *uh2; struct sk_buff *p; unsigned int ulen; int ret = 0; + if (unlikely(!uh)) {How uh could be NULL here ? My understanding is that udp_gro_receive() is called only after udp4_gro_receive() or udp6_gro_receive() validated that udp_gro_udphdr(skb) was not NULL.Right, but only after udp{4,6}_lib_lookup_skb() in certain cases. I don't know for sure if their logic can actually edit skb->data, so it's better to check from my point of view.Not really. This would send a wrong signal to readers of this code. I do not think these functions can mess with GRO internals. This would be a nightmare, GRO is already way too complex. In fact these functions should use a const qualifier for their " struct sk_buff *skb" argument to prevent future bugs.
Agree, you're right. Lack of const qualifiers gave me a doubt that these functions can't edit skbs. They really should use it if they really can't. I'll omit the check in v3.
I will test and submit this patch :
That would be a very nice one, thanks.
quoted hunk ↗ jump to hunk
diff --git a/include/net/ip.h b/include/net/ip.h index 2d6b985d11ccaa75827b3a15ac3f898d7a193242..e20874059f826eb0f9e899aed556bfbc9c9d71e8 100644 --- a/include/net/ip.h +++ b/include/net/ip.h@@ -99,7 +99,7 @@ static inline void ipcm_init_sk(struct ipcm_cookie *ipcm, #define PKTINFO_SKB_CB(skb) ((struct in_pktinfo *)((skb)->cb)) /* return enslaved device index if relevant */ -static inline int inet_sdif(struct sk_buff *skb) +static inline int inet_sdif(const struct sk_buff *skb) { #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV) if (skb && ipv4_l3mdev_skb(IPCB(skb)->flags))diff --git a/include/net/udp.h b/include/net/udp.h index 295d52a73598277dc5071536f777d1a87e7df1d1..877832bed4713a011a514a2f6f522728c8c89e20 100644 --- a/include/net/udp.h +++ b/include/net/udp.h@@ -164,7 +164,7 @@ static inline void udp_csum_pull_header(struct sk_buff *skb) UDP_SKB_CB(skb)->cscov -= sizeof(struct udphdr); } -typedef struct sock *(*udp_lookup_t)(struct sk_buff *skb, __be16 sport, +typedef struct sock *(*udp_lookup_t)(const struct sk_buff *skb, __be16 sport, __be16 dport); INDIRECT_CALLABLE_DECLARE(struct sk_buff *udp4_gro_receive(struct list_head *,@@ -313,7 +313,7 @@ struct sock *udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport, struct sock *__udp4_lib_lookup(struct net *net, __be32 saddr, __be16 sport, __be32 daddr, __be16 dport, int dif, int sdif, struct udp_table *tbl, struct sk_buff *skb); -struct sock *udp4_lib_lookup_skb(struct sk_buff *skb, +struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb, __be16 sport, __be16 dport); struct sock *udp6_lib_lookup(struct net *net, const struct in6_addr *saddr, __be16 sport,@@ -324,7 +324,7 @@ struct sock *__udp6_lib_lookup(struct net *net, const struct in6_addr *daddr, __be16 dport, int dif, int sdif, struct udp_table *tbl, struct sk_buff *skb); -struct sock *udp6_lib_lookup_skb(struct sk_buff *skb, +struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb, __be16 sport, __be16 dport); /* UDP uses skb->dev_scratch to cache as much information as possible and avoiddiff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 09f0a23d1a01741d335ce45f25fe70a4e00698c7..8b8dadfea6c9854e6bfaa0fabcb774db39976da3 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c@@ -541,7 +541,7 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb, inet_sdif(skb), udptable, skb); } -struct sock *udp4_lib_lookup_skb(struct sk_buff *skb, +struct sock *udp4_lib_lookup_skb(const struct sk_buff *skb, __be16 sport, __be16 dport) { const struct iphdr *iph = ip_hdr(skb);diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 29d9691359b9c49ccb56a11f79e3658b1a76700d..adfe9ca6f516612b5aad6d6c654c7da1dd56a50e 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c@@ -276,7 +276,7 @@ static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb, inet6_sdif(skb), udptable, skb); } -struct sock *udp6_lib_lookup_skb(struct sk_buff *skb, +struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb, __be16 sport, __be16 dport) { const struct ipv6hdr *iph = ipv6_hdr(skb);
Al