mss-bpf: rework the code to use a common skb parser header file

Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/bpf_skb_utils.h b/bpf_skb_utils.h
new file mode 100644 (file)
index 0000000..4953c86
--- /dev/null
+++ b/bpf_skb_utils.h
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Felix Fietkau <nbd@nbd.name>
+ */
+#ifndef __BPF_SKB_UTILS_H
+#define __BPF_SKB_UTILS_H
+
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/if_ether.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/ipv6.h>
+#include <linux/ip.h>
+#include <net/ipv6.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+struct skb_parser_info {
+       struct __sk_buff *skb;
+       __u32 offset;
+       int proto;
+};
+
+static __always_inline void *__skb_data(struct __sk_buff *skb)
+{
+       return (void *)(long)READ_ONCE(skb->data);
+}
+
+static __always_inline void *
+skb_ptr(struct __sk_buff *skb, __u32 offset, __u32 len)
+{
+       void *ptr = __skb_data(skb) + offset;
+       void *end = (void *)(long)(skb->data_end);
+
+       if (ptr + len >= end)
+               return NULL;
+
+       return ptr;
+}
+
+static __always_inline void *
+skb_info_ptr(struct skb_parser_info *info, __u32 len)
+{
+       __u32 offset = info->offset;
+       return skb_ptr(info->skb, offset, len);
+}
+
+static __always_inline void
+skb_parse_init(struct skb_parser_info *info, struct __sk_buff *skb)
+{
+       *info = (struct skb_parser_info){
+               .skb = skb
+       };
+}
+
+static __always_inline struct ethhdr *
+skb_parse_ethernet(struct skb_parser_info *info)
+{
+       struct ethhdr *eth;
+
+       eth = skb_info_ptr(info, sizeof(*eth));
+       if (!eth)
+               return NULL;
+
+       info->proto = eth->h_proto;
+       info->offset += sizeof(*eth);
+
+       return eth;
+}
+
+static __always_inline struct vlan_hdr *
+skb_parse_vlan(struct skb_parser_info *info)
+{
+       struct vlan_hdr *vlh;
+
+       if (info->proto != bpf_htons(ETH_P_8021Q) &&
+           info->proto != bpf_htons(ETH_P_8021AD))
+               return NULL;
+
+       vlh = skb_info_ptr(info, sizeof(*vlh));
+       if (!vlh)
+               return NULL;
+
+       info->proto = vlh->h_vlan_encapsulated_proto;
+       info->offset += sizeof(*vlh);
+
+       return vlh;
+}
+
+static __always_inline struct iphdr *
+skb_parse_ipv4(struct skb_parser_info *info, int min_l4_bytes)
+{
+       struct iphdr *iph;
+       int proto, hdr_len;
+       __u32 pull_len;
+
+       if (info->proto != bpf_htons(ETH_P_IP))
+               return NULL;
+
+       iph = skb_info_ptr(info, sizeof(*iph));
+       if (!iph)
+               return NULL;
+
+       hdr_len = iph->ihl * 4;
+       if (hdr_len < sizeof(*iph))
+               return NULL;
+
+       pull_len = info->offset + hdr_len + min_l4_bytes;
+       if (pull_len > info->skb->len)
+               pull_len = info->skb->len;
+
+       if (bpf_skb_pull_data(info->skb, pull_len))
+               return NULL;
+
+       iph = skb_info_ptr(info, sizeof(*iph));
+       if (!iph)
+               return NULL;
+
+       info->proto = iph->protocol;
+       info->offset += hdr_len;
+
+       return iph;
+}
+
+static __always_inline struct ipv6hdr *
+skb_parse_ipv6(struct skb_parser_info *info, int max_l4_bytes)
+{
+       struct ipv6hdr *ip6h;
+       __u32 pull_len;
+
+       if (info->proto != bpf_htons(ETH_P_IPV6))
+               return NULL;
+
+       pull_len = info->offset + sizeof(*ip6h) + max_l4_bytes;
+       if (pull_len > info->skb->len)
+               pull_len = info->skb->len;
+
+       if (bpf_skb_pull_data(info->skb, pull_len))
+               return NULL;
+
+       ip6h = skb_info_ptr(info, sizeof(*ip6h));
+       if (!ip6h)
+               return NULL;
+
+       info->proto = READ_ONCE(ip6h->nexthdr);
+       info->offset += sizeof(*ip6h);
+
+       return ip6h;
+}
+
+static __always_inline struct tcphdr *
+skb_parse_tcp(struct skb_parser_info *info)
+{
+       struct tcphdr *tcph;
+
+       if (info->proto != IPPROTO_TCP)
+               return NULL;
+
+       tcph = skb_info_ptr(info, sizeof(*tcph));
+       if (!tcph)
+               return NULL;
+
+       info->offset += tcph->doff * 4;
+
+       return tcph;
+}
+
+#endif

diff --git a/mss-bpf.c b/mss-bpf.c
index 5f5cb61e71dfb8135d874638a41b14188108333e..26f13ae3cabd979f2c5b29e925f7719012aa3221 100644 (file)
--- a/mss-bpf.c
+++ b/mss-bpf.c
@@ -17,113 +17,11 @@
 #include <net/tcp.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
+#include "bpf_skb_utils.h"
 
 const volatile static uint32_t mtu = 1420;
 
-static __always_inline int proto_is_vlan(__u16 h_proto)
-{
-       return !!(h_proto == bpf_htons(ETH_P_8021Q) ||
-                 h_proto == bpf_htons(ETH_P_8021AD));
-}
-
-static __always_inline int proto_is_ip(__u16 h_proto)
-{
-       return !!(h_proto == bpf_htons(ETH_P_IP) ||
-                 h_proto == bpf_htons(ETH_P_IPV6));
-}
-
-static __always_inline void *skb_ptr(struct __sk_buff *skb, __u32 offset)
-{
-       void *start = (void *)(unsigned long long)skb->data;
-
-       return start + offset;
-}
-
-static __always_inline void *skb_end_ptr(struct __sk_buff *skb)
-{
-       return (void *)(unsigned long long)skb->data_end;
-}
-
-static __always_inline int skb_check(struct __sk_buff *skb, void *ptr)
-{
-       if (ptr > skb_end_ptr(skb))
-               return -1;
-
-       return 0;
-}
-
-static __always_inline int
-parse_ethernet(struct __sk_buff *skb, __u32 *offset)
-{
-       struct ethhdr *eth;
-       __u16 h_proto;
-       int i;
-
-       eth = skb_ptr(skb, *offset);
-       if (skb_check(skb, eth + 1))
-               return -1;
-
-       h_proto = eth->h_proto;
-       *offset += sizeof(*eth);
-
-#pragma unroll
-       for (i = 0; i < 2; i++) {
-               struct vlan_hdr *vlh = skb_ptr(skb, *offset);
-
-               if (!proto_is_vlan(h_proto))
-                       break;
-
-               if (skb_check(skb, vlh + 1))
-                       return -1;
-
-               h_proto = vlh->h_vlan_encapsulated_proto;
-               *offset += sizeof(*vlh);
-       }
-
-       return h_proto;
-}
-
-static __always_inline int
-parse_ipv4(struct __sk_buff *skb, __u32 *offset)
-{
-       struct iphdr *iph;
-       int hdr_len;
-
-       iph = skb_ptr(skb, *offset);
-       if (skb_check(skb, iph + 1))
-               return -1;
-
-       hdr_len = iph->ihl * 4;
-       if (bpf_skb_pull_data(skb, *offset + hdr_len + sizeof(struct tcphdr) + 20))
-               return -1;
-
-       iph = skb_ptr(skb, *offset);
-       *offset += hdr_len;
-
-       if (skb_check(skb, (void *)(iph + 1)))
-               return -1;
-
-       return READ_ONCE(iph->protocol);
-}
-
-static __always_inline bool
-parse_ipv6(struct __sk_buff *skb, __u32 *offset)
-{
-       struct ipv6hdr *iph;
-
-       if (bpf_skb_pull_data(skb, *offset + sizeof(*iph) + sizeof(struct tcphdr) + 20))
-               return -1;
-
-       iph = skb_ptr(skb, *offset);
-       *offset += sizeof(*iph);
-
-       if (skb_check(skb, (void *)(iph + 1)))
-               return -1;
-
-       return READ_ONCE(iph->nexthdr);
-}
-
-static inline unsigned int
+static __always_inline unsigned int
 optlen(const u_int8_t *opt)
 {
        if (opt[0] <= TCPOPT_NOP || opt[1] == 0)
@@ -133,43 +31,35 @@ optlen(const u_int8_t *opt)
 }
 
 static __always_inline void
-fixup_tcp(struct __sk_buff *skb, __u32 offset, __u16 mss)
+fixup_tcp(struct skb_parser_info *info, __u16 mss)
 {
        struct tcphdr *tcph;
+       __u32 end, offset = info->offset + sizeof(*tcph);
        __u16 oldmss;
+       __u8 flags;
        __u8 *opt;
-       u8 flags;
-       int hdrlen;
        int i;
 
-       tcph = skb_ptr(skb, offset);
-       if (skb_check(skb, tcph + 1))
+       tcph = skb_parse_tcp(info);
+       if (!tcph)
                return;
 
        flags = tcp_flag_byte(tcph);
        if (!(flags & TCPHDR_SYN))
                return;
 
-       hdrlen = tcph->doff * 4;
-       if (hdrlen <= sizeof(struct tcphdr))
-               return;
-
-       hdrlen += offset;
-       offset += sizeof(*tcph);
+       end = info->offset;
 
 #pragma unroll
        for (i = 0; i < 5; i++) {
-               unsigned int len;
-
-               if (offset >= hdrlen)
+               if (offset + 4 > end)
                        return;
 
-               opt = skb_ptr(skb, offset);
-               if (skb_check(skb, opt + TCPOLEN_MSS))
+               opt = skb_ptr(info->skb, offset, 4);
+               if (!opt)
                        return;
 
-               len = optlen(opt);
-               offset += len;
+               offset += optlen(opt);
                if (opt[0] != TCPOPT_MSS || opt[1] != TCPOLEN_MSS)
                        continue;
 
@@ -190,25 +80,28 @@ found:
 SEC("tc")
 int mssfix(struct __sk_buff *skb)
 {
-       __u32 offset = 0;
-       __u8 ipproto;
+       struct skb_parser_info info;
+       u32 offset_eth;
        __u16 mss;
        int type;
 
-       type = parse_ethernet(skb, &offset);
-       if (type == bpf_htons(ETH_P_IP))
-               type = parse_ipv4(skb, &offset);
-       else if (type == bpf_htons(ETH_P_IPV6))
-               type = parse_ipv6(skb, &offset);
-       else
+       skb_parse_init(&info, skb);
+       if (!skb_parse_ethernet(&info))
+               return TC_ACT_UNSPEC;
+
+       skb_parse_vlan(&info);
+       skb_parse_vlan(&info);
+
+       offset_eth = info.offset;
+       if (!skb_parse_ipv4(&info, 60) && !skb_parse_ipv6(&info, 60))
                return TC_ACT_UNSPEC;
 
-       if (type != IPPROTO_TCP)
+       if (info.proto != IPPROTO_TCP)
                return TC_ACT_UNSPEC;
 
        mss = mtu;
-       mss -= offset + sizeof(struct tcphdr);
-       fixup_tcp(skb, offset, mss);
+       mss -= info.offset + sizeof(struct tcphdr);
+       fixup_tcp(&info, mss);
 
        return TC_ACT_UNSPEC;
 }