Re: [tipc-discussion] [PATCHv2 net 1/3] tipc: add tipc_bearer_min_mtu to calculate min mtu

[Tung Q. N. <tun...@de...>]

>As different media may requires different min mtu, and even the
>same media with different net family requires different min mtu,
>add tipc_bearer_min_mtu() to calculate min mtu accordingly.
>
>This API will be used to check the new mtu when doing the link
>mtu negotiation in the next patch.
>
>v1->v2:
> - use bearer_get() to avoid the open code.
This version change comment does not seem right. Please correct it to avoid confusion and put it after "---".
>
>Signed-off-by: Xin Long <luc...@gm...>
>---
> net/tipc/bearer.c    | 13 +++++++++++++
> net/tipc/bearer.h    |  3 +++
> net/tipc/udp_media.c |  5 +++--
> 3 files changed, 19 insertions(+), 2 deletions(-)
>
>diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
>index 35cac7733fd3..0e9a29e1536b 100644
>--- a/net/tipc/bearer.c
>+++ b/net/tipc/bearer.c
>@@ -541,6 +541,19 @@ int tipc_bearer_mtu(struct net *net, u32 bearer_id)
> 	return mtu;
> }
>
>+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id)
>+{
>+	int mtu = TIPC_MIN_BEARER_MTU;
>+	struct tipc_bearer *b;
>+
>+	rcu_read_lock();
>+	b = bearer_get(net, bearer_id);
>+	if (b)
>+		mtu += b->encap_hlen;
>+	rcu_read_unlock();
>+	return mtu;
>+}
>+
> /* tipc_bearer_xmit_skb - sends buffer to destination over bearer
>  */
> void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
>diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
>index 490ad6e5f7a3..bd0cc5c287ef 100644
>--- a/net/tipc/bearer.h
>+++ b/net/tipc/bearer.h
>@@ -146,6 +146,7 @@ struct tipc_media {
>  * @identity: array index of this bearer within TIPC bearer array
>  * @disc: ptr to link setup request
>  * @net_plane: network plane ('A' through 'H') currently associated with bearer
>+ * @encap_hlen: encap headers length
>  * @up: bearer up flag (bit 0)
>  * @refcnt: tipc_bearer reference counter
>  *
>@@ -170,6 +171,7 @@ struct tipc_bearer {
> 	u32 identity;
> 	struct tipc_discoverer *disc;
> 	char net_plane;
>+	u16 encap_hlen;
> 	unsigned long up;
> 	refcount_t refcnt;
> };
>@@ -232,6 +234,7 @@ int tipc_bearer_setup(void);
> void tipc_bearer_cleanup(void);
> void tipc_bearer_stop(struct net *net);
> int tipc_bearer_mtu(struct net *net, u32 bearer_id);
>+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id);
> bool tipc_bearer_bcast_support(struct net *net, u32 bearer_id);
> void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
> 			  struct sk_buff *skb,
>diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
>index c2bb818704c8..0a85244fd618 100644
>--- a/net/tipc/udp_media.c
>+++ b/net/tipc/udp_media.c
>@@ -738,8 +738,8 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
> 			udp_conf.local_ip.s_addr = local.ipv4.s_addr;
> 		udp_conf.use_udp_checksums = false;
> 		ub->ifindex = dev->ifindex;
>-		if (tipc_mtu_bad(dev, sizeof(struct iphdr) +
>-				      sizeof(struct udphdr))) {
>+		b->encap_hlen = sizeof(struct iphdr) + sizeof(struct udphdr);
>+		if (tipc_mtu_bad(dev, b->encap_hlen)) {
I agree that calling tipc_mtu_bad() is not necessary for UDP bearer enabling. You can remove it in this patch.
> 			err = -EINVAL;
> 			goto err;
> 		}
>@@ -760,6 +760,7 @@ static int tipc_udp_enable(struct net *net, struct tipc_bearer *b,
> 		else
> 			udp_conf.local_ip6 = local.ipv6;
> 		ub->ifindex = dev->ifindex;
>+		b->encap_hlen = sizeof(struct ipv6hdr) + sizeof(struct udphdr);
> 		b->mtu = 1280;
> #endif
> 	} else {
>--
>2.39.1